Yes, and here is how it started. Dieting became commonplace in our society when daily physical activity started to decline. By going from plowing fields and continuously walking to driving cars and pushing buttons for employment, we have cut our body’s calorie burn by more than half in fewer than 100 years. Simply put, it has become hard to believe that our bodies now run on so few calories because we seem busier than ever – and yes, you may be busier, but most of us are only “hurrying up to sit somewhere else”. Now you combine the fact that the average female in the U.S. is dieting, burning fewer than 1600 calories daily and the average overweight dieter underreports calorie intake by 40% (meaning if they say they are eating 1500 calories/day, they are consuming a daily average of closer to 2100 calories), and you have the perfect myth breeding ground.
Picture this: Mrs. Jones needs to lose weight and tells her health professional Jane that she hardly eats any food, in fact it seems less than 1200 calories/day, but Mrs. Jones is truly averaging 1800 calories while only burning 1500 cal/dy. Jane is appalled at how little Mrs. Jones is eating and thinks there is no way she can tell her to eat less than she is eating now because that would mean she would have to consume less than 700 cals/day to lose 1LB week! Jane now remembers from school that there is a metabolic adaptation the body makes when food is scarce. Unfortunately, she doesn’t have all the facts. The facts are that there is a temporary, very slight decrease in calorie burning when mammals are faced with a drastic, long-term reduction in food supply, but keep in mind that the body is definitely losing weight during this period or it would have no reason to be slowing the metabolism.
Therefore, Jane tells Mrs. Jones that she needs to eat more food in order to fire up her metabolism so she gives her a 1500 calorie/day diet but also wants her to add some kind of exercise. Now stay with me here. Mrs. Jones was eating 1800-2100 calories a day while burning 1500 leading to a steady but slow weight gain and the reason to start dieting. Jane gives her a 1500 calorie diet and tells her to move more and Mrs. Jones follows the plan. Now Mrs. Jones is burning 1800 cals/day because of exercise or increased movement, and because it’s new and she paid for it, she follows the 1500cal menus and, of course, loses weight.
Ah-ha, the myth is born: while both Jane and Mrs. Jones believe the weight loss was induced by increasing Mrs. Jones calorie intake thus firing up her metabolism, it was not. Her weight loss was a result of her actually eating 1500 cals/day and burning more and absolutely nothing else.
So the problem has never been a slowing metabolism, because starving people don't die overweight, it is simply a matter of mistaken food recording.