"Fitness myths and facts: Author chats about truth in claims, what works, and why"
 

Fitness myths and facts

Author chats about truth in claims, what works, and why

By Gina Kolata WEBMD

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Every fitness program is based on hard science and proven research. At least that’s what the books, videos, and infomercials say in bold letters. But how do you know what is true and what is hype? What will work for you? And which fitness regimens should you avoid? Gina Kolata, author of “Ultimate Fitness,” joined us to investigate the myths and facts of working out.

The opinions expressed herein are the guest’s alone and have not been reviewed by a WebMD physician. If you have questions about your health, you should consult your personal physician. This event is meant for informational purposes only.

Moderator: Welcome to WebMD Live, Gina. What led you to writing “Ultimate Fitness: The Quest for Truth About Exercise and Fitness?”

Kolata: I’ve always loved exercising. I was running before there were running shoes. I tried every group exercise fad as it came along, from Jane Fonda-type aerobics to step classes to spinning. I tried the exercise machines from Stairmasters to Lifecycles to elliptical trainers.

And along the way, like everybody who loves to exercise, I would hear the advice and the exhortations, I would hear the promises that would be too good to be true about calorie-burning or weightlifting or body-toning, and I wanted to know where did these things come from, is there science behind the advice, what should you believe, and why.

Member: That gets a bit expensive doesn’t it? Trying everything?

Kolata: Not necessarily. Running shoes are not that big an expense, and most of the other things I tried are things you can do in a gym. So we’re talking about a gym membership. My first gym was called Spa Lady. It was an all-female affair; all the equipment was pink. I bought a lifetime membership for $29 a month. My sister asked, “Your lifetime or theirs?”

Moderator: Well, which was it?

Kolata: I think it was theirs.

Moderator: What are some of the biggest “core beliefs” held by the general public about exercise that you found to be incorrect?

Kolata: I’ll give you two beliefs, one that I think is a misconception by the general public; the other that I think is wishful thinking, too good to be true.

The misperception is actually confusion over exercise goals. We’re told over and over again that all you need to do is to walk for 20 minutes a day five days a week. That’s absolutely true, if your goal is to be healthier and to live longer. But many people think that walking that amount will make them lose weight, will tone their bodies, will make them look different. That advice was never meant to be advice on how to change your weight or the way your body looks. Changing the way your body looks usually requires much more intense exercise and it takes a long time.

The too-good-to-be-true myth is one that I had believed. I had thought, and so did many people, that if you build muscle that muscle will burn more calories and fat and therefore throughout the day, even if you do nothing, even if you just sit still, you will automatically be burning more calories, your metabolism will be higher. Unfortunately, that’s not true. I asked an exercise physiologist to do a calculation for me. If a man goes to a gym and lifts weights seriously for four months he might build about four pounds of muscle, which is a lot; a woman would build much less. That four pounds of muscle would burn an extra 24 calories a day. That’s like a bite of a cookie.

Moderator: In your book, you explain in detail how you investigated a “study” that purported to make certain claims about exercise, which you showed to be baseless. How can the public know what to believe about exercise claims?

Kolata: I’d like to think that if you read my book you could learn to think for yourself about exercise claims. In general, things that sound like gimmicks really are gimmicks. In general, there’s no science behind the marketing hype, but there are basic principles that hold true.

One is the principle that you don’t have to do much to improve your health.

A second one is that to change the way you look, you have to exercise with intensity.

A third one is that exercise is not medicine, and that most people that stay with a program do it because it gives them pleasure. If you don’t like your exercise, you may want to try a different form of exercise.

Moderator: So much is presented with anecdotal “evidence” supporting claims of program success. How should we view this “evidence”?

Kolata: I would view it very, very skeptically. Usually what happens is somebody who looks good, who is young, fit, vibrant, muscular, gets up, and says, “All you have to do is X, whatever it may be, buy my treadmill, lift weights very slowly or whatever this person is saying, and you too will look like me.” Then you will have testimonials, the before and after pictures. I do not consider any of this evidence at all; this is marketing.

Member: I just joined a gym. Some of the machines have heart rate and fat burning rates on them. What are these? Is there really a “fat-burning zone”?

Kolata: The fat burning zone is a myth. The idea is if you exercise slowly you burn more fat than if you work out more vigorously. It’s absolutely not true, and I explain why in my book. The cardio programs on the machines are usually pretty mild exercise programs based on the idea that for your heart you don’t have to do much.

All these programs, as I see it, are marketing tools. You certainly should not take them seriously, because even the heart rate formula that is behind them is unreliable and highly inaccurate.

Moderator: So much of what we do is based on Dr. Kenneth Cooper’s aerobics work. Do you think his basic premise is valid?

Kolata: His basic premise has changed over the years. He used to say that you don’t have to lift weights; now he says lift weights. He had a formula to compare exercise intensity, which few would say was accurate; however, he was an exercise evangelist. He encouraged thousands of people to try exercise, and so in a way, he is a hero of the exercise movement.

Member: Years ago, 20 minutes of exercise three times a week was recommended. Then it went up to 25 minutes; then to 30. Is there any scientific basis for this “inflation?”

Kolata: Actually, most recently it went up to 60 minutes. The reason is, once again, what are your goals? When they told people 20 minutes, many public health officials thought that people were cheating. One researcher said to me, everyone overestimates how much he or she exercises and underestimates how much he or she eats. So some of the inflation is an effort to get people to maybe do just 20 minutes of exercise. The 60 minutes is somewhat different. There the idea was, we tell people they have to eat all these different foods, fruits, vegetables, dairy products, protein, and if they take us seriously, they’ll get fatter than ever. Believe it or not, this was the reasoning that the National Academy of Scientists, when its committee said now you should walk 60 minutes a day.

Member: Some life extension research suggests that caloric restriction is key to longevity. Some of this same research has indicated that lower levels of exercise are more beneficial to longevity rather than “extreme” exercising. I know this may be out of your area a bit, but have you heard this?

Kolata: It’s very hard to know whether caloric restriction increases your life span, because in some animals it may, and some animals it may not. We have no idea about humans. The same goes for extreme exercise. The way we know that moderate exercise helps is by looking repeatedly at huge groups of people, thousands or tens of thousands of people and following them over the years and asking whether exercise is associated with a longer life span, and, if so, how much exercise. Very, very few people are extreme exercisers, and so it is impossible to know what is cause and what is effect when you have so few people and so little data.

Moderator: When we try to evaluate claims made by various exercise programs or trainers, what are the key factors we should consider? Is there any institutional “seal of approval” that would give some indication of validity?

Kolata: These programs and the trainer certifications are almost exclusively marketing tools. And as one exercise physiologist said to me, it’s a jungle out there. One group, the American College of Sports Medicine, has a rigorous certification program for instructors. But in the end, I think you have to ask yourself, what are my goals? And if the program or if the instructor does not understand your goals or is not helping you to achieve them, you should not think they have some secret knowledge or expertise that you lack, and use that as a reason to stay with them. In other words, I think you should use common sense if you don’t think something is working and you do not trust the person that is promoting it to you, you should not stay with them.

Member: So, what did your research find to be the ultimate exercise program in terms of time, type, and intensity?

Kolata: It depends on your goals. If your goal is to change the way you look, then the ultimate exercise program would be one that is strenuous and regular. You have to keep at it. But I think the ultimate exercise program is one you enjoy. And if high intensity makes you feel good, that’s your ultimate program. If you hate it, it’s clearly not for you.

Member: What about the claims you see on bodybuilding supplement products, like those protein powders and creatine? They sell a lot of this stuff to teen boys who want to get “cut.” Is any of it worth the can it comes in?

Kolata: I don’t think so. In fact, I have a whole chapter on bodybuilding and its history. And you will see that the idea of selling protein supplements began half a century ago and was pure marketing from day one. In fact, at one time the Federal Trade Commission told the inventor of this marketing gimmick to take the muscle man off of the label of his protein supplements, because people thought if they ate the protein they would look like the muscle man. I worry about some of these supplements. My friend’s son takes them, and when I looked at the ingredients of one, it included not just proteins, vitamins, and minerals, but an herb that was supposed to be a testosterone precursor, and raw prostate extract and raw testicular extract. It didn’t say what animal these extracts came from.

Moderator: The point of your book is to get people to think for themselves regarding fitness and exercise.

Kolata: That’s right, it is. I’m not selling a magic program, but I think if you can pull aside the veil over the fitness industry, you can then understand the basic principles of how to gain strength and endurance and how to understand your own fitness goals and how to achieve them. Then I think you don’t need the magic program, because you can think for yourself.

I also hope that people will learn to love exercise when they realize that for many of us, it is a source of pleasure, and sometimes it’s just a matter of finding which exercise is most appealing to you.

Moderator: Why do you think people are so willing to try so many different fitness programs with outrageous claims — claims that they would probably be skeptical of if applied to another area of life?

Kolata: We want to believe the myths. It’s the same psychology that occurs at the cosmetics counter when someone tells me, “Oh, just buy this cream and it will get rid of the wrinkles around your eyes.” When you see somebody who looks good and tells you it’s easy, it’s all too enticing sometimes to raise questions. When the program doesn’t work, we usually assume it’s because we didn’t do it right or we gave up on it too soon.

It’s a lot like diets. If there were the perfect diet nobody would be fat in this country. And yet year after year we dash from one diet to the next, each one claiming to be scientific and to have an amazing way to melt off the pounds and testimonials, once again, are accepted as evidence.

Moderator: Do we have unrealistic expectations, expectations that exceed the limits of biology, in part because of media images?

Kolata: I think that often we do. In fact, people vary along a bell curve in their ability to respond to exercise. That’s one thing I discovered on working on this book, and just like most of us will never be champion athletes, no matter how hard we train, there also is a limit to how much exercise can do for us in changing the way we look. I do think it can make us healthier, I do think it can change the way you feel, it can change your mood and it can change the way you feel about your body. But dramatic transformations are unlikely for most people.

Member: When you were researching your book, did anything you discovered surprise you?

Kolata: I was really surprised along the way when one myth after another fell. I hate to say it, but I was really surprised when I learned that putting on muscle does not increase your metabolic rate. I was really surprised that the maximum heart rate formula was so wrong. I was really surprised that some things that do work, like interval training, were discovered by coaches by trial and error. I guess along the way the more I looked into this the more my eyes were opened. And the smarter I became about my own susceptibility marketing hype.

Member: Should we make sure fun is part of our exercise?

Kolata: I would say yes. Over and again as I worked on this group I asked people why do you exercise. Over and over again it was the same answer: It makes me feel good, I like the way I feel, it’s become part of who I am. One man told me that the idea of not exercising is like saying “I think I won’t brush my teeth anymore;” it was that much a part of daily life.

I did find one man, and only one, who said he had been exercising for years and hates it. I asked him then, “Why do you exercise?” and he said, “It’s out of fear.” He had had a heart attack and begun a cardiac rehabilitation program. It required walking around a track with a group several days a week. He’s been with it for decades, but he said, most people drop out. He then did admit one thing to me. Before they walk on the track the group lifts weights. This man said he didn’t really mind lifting weights. Then one day, to his enormous surprise, he was on an airplane and he had to lift his bag into the overhead rack; he could not believe how easy it was. He told me this gleefully. Somehow, that part of exercise had given him some pleasure. Some psychiatrists told me that they actually prescribe exercise to their depressed patients. I do think it can lift your mood.

Moderator: Gina, we are almost out of time. Before we wrap up for today, do you have any final comments for us?

Kolata: This is the way I end my book and I think it sums up the message:

One day, I get an email from Richard Friedman, the avid swimmer and psychophamarcologist at the Cornell Medical School. He knows I’m writing this book and he has a question: “Are you planning to tell the truth about exercise?” he asks me.

I write back. What, I ask, is the truth?

“Ah, the truth about exercise?” he replies. “Well, I suspect that exercise is more often a marker of health than its cause — healthy people like to exercise more than unhealthy people, to start with. And the real value of it is not in terms of abstract health benefits like longevity — an extra few hours or maybe months — but because it feels good when you do it or when it’s over. To hell with Hygeia; the truth lies in pleasure.”

Moderator: We are out of time. I’m sorry we couldn’t get to all of your great questions. Our thanks to Kolata, and thank you members for joining us today. For more information, please read “Ultimate Fitness: The Quest for Truth About Exercise and Fitness” by Kolata. Please visit the WebMD Fitness and Exercise Center and the message board, Exercise and Fitness: Richard Weil, MEd, CDE.

Gina Kolata is a science reporter for The New York Times and the author of four books including “Ultimate Fitness: The Quest for Truth About Exercise and Health”.

WebMD content is provided to MSNBC by the editorial staff of WebMD. The MSNBC editorial staff does not participate in the creation of WebMD content and is not responsible for WebMD content. Remember that editorial content is never a substitute for a visit to a health care professional.

New Here
 

can anyone tell me if creatine is ok to use during low carbing?
THANKS KRISTINE :) BUT IM TOTALY NEW HERE.. WHATS A THREAD? WHERE IS THE GENERAL FORUM AND WHERE IS THE GLOBAL SEARCH THINGY PLEASE .. THANKS

Oh, this one's scary! They give us the pyramid, realize it's making us fatter and so tell us to exercise to offset their mistake rather than take back the pyramid. Of course she left starches (the base of the pyramid) off her list of foods. :roll:

I used to work out a LOT.
I enjoyed it, but I was a size larger then than I am now doing low carb eating, living on the third floor, and parking away from the door of the supermarket.
How does that fit into the equation?

Interesting article. :thup: I'm surprised by her conclusion about the muscle mass / metabolism thing. :confused:

adkpam, that's my case, too. :thup: I don't even have a car. My exercise routine involves walking just about everywhere, including home from the grocery store with 20 lbs of groceries on my back. My motivation? If I don't do it, I starve! :lol:

bumpstone, I bet there are lots of threads on creatine in the General Exercise forum. :thup: If you don't see any, you can click on the to do a search. :cool:

Doesn't seem to fit into the equation does it?
 

Along the theme that adkpam mentioned - before I did LC WOE I was a size larger and no amount of excersize "I did" helped me lose weight. I kept hearing about the increase muscle mass burn more calories deal. Then you must excersize for the first 1/2 hour free of charge no gain there - only after that first 1/2 that you then burn fat.

Was not until about 4 years ago at a new gym - they taught me about interval training. Still all that did nothing to stop my weight gain.

I will say for my case - only the LC diet took the lbs of and it did it in a hurry. No excersize was involved.

Now I excersize more and like the feeling - but still cannot tie excersize to my weight gain or loss. I control my weight exactly with how much sugar I eat even in the LC form. I have had real good results maintaining but I use the scale almost every day to check where I am at.

Most people just cannot spend enough time per week to excersize enough to make a weight difference. It is a pidly small amount of calories burnt for the effort compared to what you can shovel in or not shovel in your trap! :yay:

It took me 5 years to lose 10 kilos. The first 5 kilos took about a year with up to 8 hours a week at the gym and giving up nearly all fats, dairy etc. and eating what I thought was a healthy (high carb) diet. I could absolutely not shift anymore weight no matter how much exercise I did.
The second 5 kilos took me 5 weeks.....the first 5 weeks on Atkins induction and I was too tired to do any exercise at all!
Now my weight's steady with 30 mins walk every day and the low carb diet.

I really must disagree with her there. From personal experience, I can safely say that building muscle (especially lifting) has helped me make leaps and bounds in my dieting goals. The "study" she speaks of seems wrong.

Ok, let's wait for the exercise fanatics to get ahold of this thread. I suspect they will attack it just the way the medical establishment has attacked the Atkins diet. People will not be able to accept that building muscle mass doesn't have a profound effect on (every)one's metabolism.

I think one of Kolata's most interesting points is that there's a bell curve in terms of how much individuals can benefit from exercise. The people who befefit the most (and the quickest) become hooked and then are convinced that there is no other way to lose weight and maintain the loss. I have wondered why Dr. Atkins himself became so convinced that exercise was necessary (as opposed to desirable). Anyone know?

I think that hundreds of years from now people will look back on our gyms and fitness centers the way we now look at the thermal baths of the 19th century or other health spas of the past: their social function will be more important than their actual contribution to health.

Having said that I certainly believe (and have seen the evidence) that for many people vigorous exercise and weight training can transform their bodies. But the committment required is outside the realm of possibility for most.

Necessary for weight loss, or necessary for health? I'm with the others here who haven't found exercise necessary to lose weight -- but I don't think humans can be said to be healthful when they don't exercise. Is that maybe what Dr. Atkins meant?

Exercise has demonstrable good effects on the body, especially in our present environment. And I'm convinced Dr. Atkins was determined for people to succeed on his plan (bless his heart) and pushing exercise is one way to ensure that.
I plan to exercise more myself, because I enjoyed it and liked it when I could fit it into my schedule. And I think people are more likely to exercise when they are slimmer and feel better.
The big thing about pushing exercise, from the mainstream, is that it is the only hope of people burning up all those carbs they eat, and showing a weight loss on low fat/high carb!

Exercise is a must.
 

Exercise is a very important part of being a healthy person because it is what our bodies are designed to do. It is universally agreed across all different philosophies and doctrines of wellness that exercise is beneficial, moreover integral.

The most recent studies show that vigorous exercise for 30 minutes a day is extremely beneficial to counter heart disease and (short of LC'ing) one of the key ways to keep blood sugar under control for diabetics.

Weight lifting has been shown to strengthen bones and joints. I know that Tae Bo and weights have kicked the early signs of arthritis that I had, gave me more energy, and boosted my mood.

However, "exercise" does not necessarily mean getting a gym membership and pumping a lot of iron. I think that we forget that exercise (aerobic and otherwise) can be as simple as walking more, gardening, and playing outside. Remember when playing outside was fun? Swinging, monkey bars, tag, frisbee, hiking, swimming.. these things are all natural to us when we are kids, but for some reason as we get older we forget the fun of exercise.

Our bodies were not designed to recline on a proverbial couch or sit in front of a computer for 40 hours a week, but rather to do many different types of tasks as our hunter-gatherer ancestors would do.

This is an old thread I found using the search function, however since I'm new to the forum this is new to me and I have some comments.

Even if the basic point that building extra muscle does not burn an appreciable extra amount of calories is true (no more than a cookie per day, for instance) and even if exercise only adds a few months to one's lifespan (which I question, I would think it adds much more) still there are other benefits from exercise beyond weightloss.

For one, there's the quality of life. Exercise, particularly strengthtraining can keep one from losing bone mass in later life, can strengthen joints, delay or minimize the effects of arthritis. You can still do those hikes through the mountains or climb the stairs for many more years that one who doesn't exercise. In other words, the Quality of Life improves significantly even if the length of life only increases a little. Then, as the author says, you can look a lot better in a swimsuit or anything else with intense exercise.

I have read other articles that also state that exercise adds only a few months at best. But like Mithridate, I also believe that exercise greatly increases the quality of one's life. I know people in their 80s who have never exercised and have been unhealthy and full of aches and pains for years. They take lots of medicines for all sorts of aliments. I also know people in their 80s who have exercised most of their lives and are still active and healthy and fully enjoying life and not on drugs (a much small number of people). I would much rather be in the later group. Of course I am one of those who enjoys exercise.

I enjoy riding my bike. ;)

To me my point in all of this is to do what you like and what works for you, i can say that whey protein and greens plus helped me grow thicker hair, after a big period of stress.

Only thing is when it sounds to good to be true it surely isnt.

The part where she says it should be fun is right, makes me think of so much people that go to the gym but dont even like it, then quit.

Low carb works and it works amazingly well, with age it gets toughter to lose weight but with low carb i can still lose a tone, sensible eating made me lose around 5 pounds in 4 months which is a joke, but low carb made me lose 35 pounds in the same amount of time.

When I started low-carbing I was unable to exercise due to arthritis in my knees and feet, asthma, and excess weight. After 6 months of low-carb eating alone (without exercise), my arthritis almost completely disappeared, my asthma inproved, my strength improved and my energy levels skyrocketed so that I am able now to exercise moderately. Diet plays the largest role in a person's health. Exercise is secondary.

I so agree. When I started low-carbing, I couldn't walk down the hallway at work without feeling totally exhausted. There was no way, at that time, that I could exercise. I had asthma, no energy, and I ached all the time. After about a month of low-carbing, my asthma was gone and I was feeling so good that I started walking. Later, I added in hiking and dancing. And now lately, I've added bike riding to my activities. IMNSHO, I could not have done any of that without low-carbing.

I am very suspicious of the 'experts' who calculate how many calories each pound of muscle will burn and then pronounce that adding muscle has little effect on weight loss or maintenance. It sounds very much like those experts who assure us that it is impossible to lose more weight with a low carb diet than with a low fat diet. You know, the old 'a calorie is a calorie' bit. Human bodies are not test tubes, and what goes on in our bodies is not as simple as some controlled reaction in a lab.

I won't be at all surprised to read some day that added muscle has some thermogenic effect that does indeed burn more calories in the human body.

http://www.pponline.co.uk/encyc/0120.htm

Metabolic Rate And Exercise: Researchers have been trying to puzzle out the effects of exercise on energy expenditure (calorie burning) for decades.

Despite an ever-growing mountain of research documentation, the exercise/calorie-burning story is still far from clear. There's some evidence that exercise can boost your metabolic rate - but, confusingly, regular activity appears to LOWER metabolic rates for some people. Here is a summary of the findings so far, and a round-up of the latest most-popular explanations of just what is going on.

To decode the research, there are some basic definitions to grasp first. In any 24-hour period,we burn a given number of calories - that's referred to as the total daily energy expenditure (TDEE). This total is made up from a number of different types of energy expenditure. For a start, there's energy used up by the Resting Metabolic Rate (RMR), the amount of calories burned just to keep you alive, with all your bodily systems ticking over. This accounts for a big chunk - 60-75% - of total daily energy expenditure.

Secondly, have you noticed that eating tends to warm you up, even when you're eating cold food? Cue the Thermic Effect of Feeding (TEF), the extra energy burned during and after eating anything. This effect is due to the work involved in absorbing food, digestive enzymes getting busy, increased blood flow, and so on. This takes care of about 10% of daily energy expenditure. Finally, physical activity uses up calories. Activity includes formal exercise, as well as 'casual' movement, such as fidgeting or shivering! This component generally constitutes between 15 and 30% of daily energy expenditure.

So - exercise increases calories used due to the need to fuel extra activity at the time. But the question that has kept scientists fascinated (and, as yet, stumped) is: does exercise have an impact on the other calorie-burning mechanisms? Will a jog or an aerobic dance session zap up the amount of energy you burn as you sleep? The answer so far? Maybe.


Aerobic exercise: acute effects
A number of studies have found that aerobic exercise increases energy expenditure in the period of time immediately after activity. But there may be a threshold to clamber over before the effect kicks in. Light aerobic exercise (around 50% VO2max) seems less likely to make a difference, while moderate or intense are more likely to. For example, one review concluded that light exercise could be expected to lead to burning an extra 5-10 calories afterwards; moderate to an extra 12-35 calories. In contrast, strenuous exercise was shown to increase post-exercise energy burning by a huge 180 calories ('Excess post-exercise oxygen consumption - magnitude, mechanisms and practical implications', Bahr et al, Acta Physiol Scand, suppl 605, pp 1-70).

Overall, there's pretty convincing evidence for an acute effect of exercise on energy expenditure. Most studies that have found an elevated resting metabolic rate have made their measurements within 24 hours of the exercise session. One investigation found that any post-exercise increase in RMR faded between 24 and 39 hours. Looking at the information available at present, it seems that to SIGNIFICANTLY boost energy expenditure after exercise, the activity needs to be intense (over 70% VO2max) and prolonged (over 90 minutes); the effect will be most pronounced in the first 12 hours post-exercise.


Long-term training effects
Some investigators have focused on long-term training, trying to find out if athletes who take part regularly in endurance exercise have their metabolic rates affected. This is different from looking at the immediate effects of a one-off exercise session. One expert reviewed the evidence and concluded that metabolic rate is between 5 and 19% higher in highly active compared to sedentary individuals ('Impact of energy intake and exercise on resting metabolic rate', Mole et al, Sports Medicine, vol 10, pp 72-87).

But there may be a gender difference in the metabolic response to exercise. The majority of studies have focused on men. What research there is on women does not convincingly support a difference in RMR between trained and untrained women. At least four studies which looked at both men and women found that total daily energy expenditure did not significantly increase following training in women, but did in men. It appears that women conserve energy more efficiently (ie, they burn fewer calories) at rest and in response to exercise.


Resistance exercise
Resistance exercise is any activity that increases your muscle mass, such as weight training; sports such as cycling and rowing also have resistance elements. There's not so much research data available on this type of activity compared to aerobic exercise. But emerging evidence suggests that resistance exercise is capable of boosting your overall calorie burning.

Muscle tissue burns more energy just ticking over than does fatty tissue. Therefore, increasing your muscle:fat ratio would be expected to give you a higher resting metabolic rate.

Dr Catherine Geissler is a nutrition expert at King's College, London, with a special interest in how the body uses energy. She estimates that the increased lean body mass associated with exercise can increase total daily energy expenditure by between 8% (143 cals per day) for a moderately active person to 14% (286 cals per day) for a highly active person.

Does resistance exercise have an effect beyond the simple one of altering the muscle:fat ratio? So far, the story isn't clear. Eric Poehlman, an expert in metabolism from Maryland University, reviewed the research results on the effects of resistance exercise ('Effects of exercise on daily energy expenditure', Poehlman & Toth, Nutrition Reviews, vol 54, pp S140-149).
He concluded that resistance training has an effect on resting metabolic rate (independent of any change in muscle mass) for the over-50s but not in younger individuals. This type of exercise may therefore be an effective way to offset the decline in total daily energy expenditure which typically occurs with age.


The role of energy efficiency
Some investigators have found LOWER metabolic rates in highly active athletes. One way of making sense of this apparent contradiction is to take into account two related factors: energy balance and energy efficiency.

Here, 'energy' means the energy available from food, measured in calories. When the amount of energy you take in (calories consumed) is equal to the amount of energy you use up (calories burned), you're said to be in 'energy balance'. If you're burning more calories than you eat, you're in 'negative balance'; conversely, eating more calories than you burn puts you in 'positive balance'.

Some experts believe that being in a state of negative energy balance puts your body into a special energy-conservation mode. In other words, the body believes that there's a scarcity of calories, and it has to conserve what energy is available. This is made possible because there is some leeway in terms of how energy-efficient our metabolism is. In a less efficient mode, the body can be quite wasteful with calories, performing metabolic tasks in a way that uses up a lot of energy. In an energy-conserving mode, essential bodily functions are carried out at minimal energy cost.

It's probable that there are genetically-determined differences between individuals in terms of how energy efficient their bodies are in general. But the degree of efficiency also seems to be influenced by whether the body thinks there's a scarcity or abundance of calories available. Thus, some athletes report having to eat LESS to maintain their ideal weight as their training duration increases. It seems that their metabolic rate slows to conserve calories as a defence mechanism, similar to the way metabolism slows in slimmers as a defence against starvation. One way to avoid this effect is to eat more if you're exercising more - that way you're less likely to get into a downward spiral of having to eat fewer and fewer calories to maintain the same body weight.


How does exercise have an effect?
When exercise does boost total daily energy expenditure, there are a number of potential mechanisms:
1. Increased hormonal activity Some invest-igations have found that increased resting metabolic rate following endurance exercise is associated with higher blood levels of adrenaline and noradrenaline. These hormones are controlled by the nerves embedded within muscles, known as sympathetic nerves. Some scientists have looked directly at sympathetic nerves in muscles and found that exercise stimulates the nerve activity. These hormones tend in turn to stimulate various metabolic processes which have the net effect of raising RMR. Other hormones may also play a role. There's some evidence that exercise leads to an increased production of thyroid hormone, which in turn steps up general metabolic activity.

2. Protein resynthesis Several lines of evidence suggest that increased metabolic rate following exercise is associated with altered protein metabolism. Some data show that exercise increases protein breakdown. To keep protein status constant, protein synthesis would need to be stepped up following exercise. There's some indication that exercise causes an increase in the levels of enzymes involved with making proteins. However, so far there's no direct experimental evidence confirming a direct link between increased protein turnover and metabolic rate.

3. High energy flux Two individuals can both be in a state of energy balance, but the number of calories being consumed and burned can be vastly different. A number of researchers believe that the concept of 'energy flux' is all-critical. Basically, a high energy-flux state exists when the increase in calories burned due to an exercise programme is coupled to an increased intake in calories.

For example, one study looked at young male volunteers whose activity levels and calorie intakes were strictly controlled over a 10-day period ('Effects of increased energy intake and/or physical activity on energy expenditure in young healthy men', Goran et al, J Appl Physiol, vol 77, pp 366-372). A significant increase in RMR was seen in the volunteers who were in energy balance at a level of high energy flux. Therefore, increases in RMR may occur following endurance exercise training if dietary intake is stepped up to match the increased caloric expenditure of the exercise.

4. Activity generates even more activity Apart from any direct effects on metabolic rate, there's some evidence that exercising regularly boosts general physical activity throughout the day. Put simply, the fitter you are, the more energetic you're likely to be in your daily life, attacking your daily tasks with extra gusto! For instance, one study found that three young men showed a significant increase in total daily energy expenditure after nine weeks of endurance training. These men had unaltered RMR, and the increased energy expenditure was put down to increased general physical activity.


Conclusions
Despite a huge amount of literature on the subject, differences in experimental procedures mean it's hard to make meaningful comparisons and draw overall conclusions. So far we can only make educated guesses:
1 Exercise may significantly increase metabolic rate for between six and 36 hours after exercise
2 There may be a threshold effect for intensity and duration - possibly 70% VO2max, for 90 minutes or longer
3 Regular endurance exercise may boost levels of activity during the rest of the day
4 Gender seems to be a factor; women's metabolic rates seem less affected by exercise
5 Resistance exercise may be a good way to offset the declining metabolic rate typically found as age increases
6 Going on a strict calorie-restricting diet as well as stepping up exercise may not work as a way of losing weight - you could be better off eating more.

Janet Stansfeld

Then don't be surprised, because it does.

Now, I'm not going to say that each pound of muscle raises your basal metabolic rate by exactly 50.22323 kcal.

But consider this: If muscle didn't burn any extra calories, why is your body so prone to attack it when you don't get enough food?

Proof by contradiction. QED.

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