Two weeks ago the results of following contestants from the 2009 season of The Biggest Loser was published. It caught the news and was widely reported as the failure of dieting. The New York Times did a slightly better job - but there is more to think about.
Trying to work out the energy balance of eating - energy in and energy expended - is something of a fool's errand. The fundamental understanding of metabolism is lacking. It is possible, under careful laboratory conditions and using expensive techniques, to get the numbers right. What is found is the body can vary its efficiency. There is a connection that probably goes in both directions between the body you think of and your microbiome. The existence of a set-point - a weight your body to be at - hasn't been proven, but more than a few experiments suggest that you'll have difficulty maintaining a new weight after a large weight loss. The result reported two weeks ago has been seen in other studies. It also must be pointed out that large weight loss appears to be more difficult to maintain, but about ten to twenty percent of dieters who have lost a significant amount of weight have been able to control their weight over the long haul.
Some well established bottom lines are that you usually can't outrun your fork. Exercise is fantastic medicine by itself that is more powerful and effective than many of the drugs people take with few side effects. Just do it, but don't expect to lose weight. You can maintain weight with effort, but if you've lost a lot it can be extremely difficult. There aren't any magic bullets or diets, although some interesting signals are emerging.
We're alone among the great apes when it comes to body fat. Few of the other guys exceed three percent body fat and some are below one percent. It turns out we need much more energy, pound for pound, than the other apes. It has only recently been studied, but are resting metabolic rates are much higher - about 400 calories more than chimps, 650 than gorillas and over 800 more than orangutans.1 We need to do this to support our large brains - your brain accounts for about a fifth of your resting metabolism - and to have the ability to have more offspring. Along the way our bodies developed a kind of range anxiety - we can't let ourselves run out and developed the capacity to store a lot of energy in the form of fat. Most of our history had periods of food insecurity and we evolved to store energy whenever we can. Now that many of us have enough we're learning how difficult it is to fight our own biology.
These studies came as I was thinking about a terrific special April 29th issue of Science on the microbiome. Our relationship to it, or more properly another part of ourself, is tied into many things... notably metabolic disease and obesity. A bit of serendipity - I happened to catch Christina Warinner's SciCafe talk at the American Museum of Natural History a few months ago. She's a molecular anthropologist and has been working out how our microbiome evolved along with us. A terrific overview with some parts on food.
1 The study adjusted for body size and took into account activity levels.