Saturday, January 16, 2010

When dieting doesn't work

Ok I know this is monkeys, but it is still interesting (but not really new)

Put monkeys on a diet and they do not lose weight because their activity levels fall to balance the reduction in food calories in. The body defends against weight loss from a diet by doing less.

Eat less and you will do less? The other side of this is the position Taubes takes - do more and you end up eating more anyway. (Especially with a calorie bomb recovery shake!)

Also note that it was a low fat diet - I wonder what the macros were for it? Often you find lab chow to be real junk - lots and lots of sugar and PUFA.

This is actually a rather depressing study the implication being that if you want to lose weight then you must:

  • run on a treadmill for 1 hr/day, 5 days/week at 80% maximal capacity

Honestly it does't have to be that hard. (Remember Martin) There is a more natural way!

A Rapidly Occurring Compensatory Decrease in Physical Activity Counteracts Diet-Induced Weight Loss in Female Monkeys.
To study changes in energy balance occurring during the initial phases of dieting, eighteen adult female monkeys were placed on a low-fat diet with a 30% decrease in calories for one month. Surprisingly, there was not significant weight loss, however daily activity level (measured by accelerometry) decreased soon after diet initiation and reached statistical significance by the fourth week of dieting (18+/-5.6% decrease, p=0.02). During a second month of dieting, caloric intake was further reduced to 60% of baseline consumption, leading to 6.4+/-1.7% weight loss, and further suppression of activity. Metabolic rate decreased by 68+/-12 kcal/day; with decreased activity accounting for 41+/-9 kcal/day, and the metabolic activity of the weight lost accounting for 21+/-5 kcal/day. A second group of 3 monkeys was trained to run on a treadmill for 1 hr/day, 5 days/week at 80% maximal capacity, leading to increased calorie expenditure of 69.6+/-10.7 kcal/day (equivalent to 49 kcal/day for 7 days). We conclude that a diet-induced decrease in physical activity is the primary mechanism the body uses to defend against diet-induced weight loss, and undertaking a commonly prescribed exercise program for people seeking to improve fitness is sufficient to prevent the compensatory decrease in physical activity-associated energy expenditure that slows diet-induced weight loss.

Read more on these ideas at the Science of Sport blog here


Anonymous said...


There's another way to look at this too - if you eat more you will do more, i.e. eating a lot is a way to raise the metabolism. You won't necessarily lose or gain weight, but it may be that you would prefer to have a high metabolism at a given weight rather than a low metabolism at a given weight. Or maybe not.

mc said...

Yes and no. this is all so single factor.

Eating less only works if it creates a caloric deficit. C'mon.

Most people gain weight BECAUSE they are eating way more than we need either for maintenance or for health.

The equation is pretty simple. even more so if you're a couch potato who can't do less.

Eat less than you need for maintenance of CURRENT activity levels and you burn more body fat for fuel. Slow down, create less caloric deficit, burn less.

Most of us if we're doing as little as we can actively can't do less.

thermodynamics still and always applies.