I think that's probably your problem. You're likely not eating enough. The idea of low carb isnt' to starve. It's
not low calorie, especially in the beginning. You should eat at least 3 meals a day, I prefer 4-5 smaller meals. Set a schedule and eat when it's time to eat, hungry or not.
Drinking plenty of water is very important too!
The heatrate problem I'd say is because your body is working harder, trying to exercise without enough calories. If this doesn't clear with increasing your calories, I'd suggest a call to your doc, especially if it's also elevated at rest or you're having palpitations (fluttering or pounding).
Typical day for me:
Breakfast: EAS low carb ready to drink with 1/2 cup egg beaters and 4T flax seed.
Midmorning: small salad or celery with cream cheese or small amount meat/egg with veggie.
Lunch: large salad with chicken, full fat dressing, sometimes a little grated cheese.
Midafternoon: similar to midmorn
Supper: meat/fish/poultry with higher carb veggie like broccoli, brussel sprouts.
(Mind you, breakfast is around 7 or 8 AM, supper isnt' until 8 or 9 PM.)
I also drink at least 3 quarts of water each day.
Supplements: most people suggest at least a good multivit, potassium (recomended dose only!), Calcium and Magnesium.
Try increasing your intake, that might help.
Cindy