I'm not a petite female either but I'll comment too: IR may factor in somewhat at least in the beginning of a lowcarb diet. Typically in insulin-resistant persons the insulin levels are high. Insulin blocks ketosis. Therefore, someone with insulin resistance may have, at least initially, a lousy time getting used to a lowcarb diet. Once the insulin drops this should subside. How long this takes and how important this effect is - don't know, but we've tossed this around on the lowcarb list a while back and agreed that it may matter.