I have heard several conflicting theories about going into starvation mode when someone is not eating enough calories for their activity level. There are people that say this is correct and there are others that argue it is B.S and say that a person will still lose weight even if they are not eating enough calories. What do you think? (I would rather ask a bunch of professionals such as yourselves than read any more comments in a bogus comment feed).
I suspect that you’re referring to the so-called “hypothalamic set-point” theory. Theory is the key word. The reality that such a physiologic response occurs in response to hypocaloric dieting is certainly debatable. I try to keep an open mind and trust in my education and experience.
It is my opinion that the literature is correct in suggesting that if total energy(calorie) intake is less than energy output weight loss will be the ultimate result. However, this negative energy balance and its physiologic effects are significantly impacted by several factors.
If calorie intake (with proper distribution of the six basic nutrients) is sufficient to satisfy resting energy metabolism (RMR) needs and the negative balance is a result of exercise (primarily cardiovascular and resistance training) and activities of daily living the weight loss will be primarily from lipids stored in adipose cells (the body’s primary energy reserve.) Lean body mass (LBM) will, for the most part, be maintained. If total weight loss is more than 40-50 pounds LBM will decrease since that muscle is no longer needed to support the body’s weight.
If the negative energy balance is a result of inadequate calorie intake to support even RMR (starvation) the body will mobilize not only its fat reserves, but will utilize skeletal muscle and organ proteins to generate the glucose it needs for cytoplasmic and mitochondrial ATP production (gluconeogenesis.) This is, obviously, not healthy weight loss.
If your question is focused on effective, healthy weight loss, the take away for me is to suggest to your client(s) that moderate calorie reduction, maintaining an adequate diet of mostly the right kinds of foods most of the time, coupled with
frequent, vigorous exercise will likely be the most effective approach in the long run. Keep in mind that the research is clear in suggesting that maximum effective weight loss over time is 1-2 lbs/wk. Adequate water/fluid intake and plenty of sleep are critical.