Exercise & Weight Management
I've been having a little discussion of this over at Taubes' forum based on his comments on the Dr. Oz show. He basically regurgitated two points that he's never really offered up much scientific proof of:
1. Exercise just makes you hungry, and
2. You'll compensate for the increased activity during exercise by lazing around the rest of the day.
On point 1, Taubes loves to use the "have you ever heard the phrase working up an appetite" line. At least he sounded a little less condescending asking that this time as compared to when he asked Jillian Michaels in his 2007 Larry King appearance.
In a "I think I gotcha moment", one commenter posted this study as evidence of eating more: (I only have the abstract for this one):
The efficacy of exercise to promote weight loss could potentially be undermined by its influence on explicit or implicit processes of liking and wanting for food which in turn alter food preference. The present study was designed to examine hedonic and homeostatic mechanisms involved in the acute effects of exercise on food intake. 24 healthy female subjects were recruited to take part in two counterbalanced activity sessions; 50 min of high intensity (70% max heart rate) exercise (Ex) or no exercise (NEx). Subjective appetite sensations, explicit and implicit hedonic processes, food preference and energy intake (EI) were measured immediately before and after each activity session and an ad libitum test meal. Two groups of subjects were identified in which exercise exerted different effects on compensatory EI and food preference. After exercise, compensators (C) increased their EI, rated the food to be more palatable, and demonstrated increased implicit wanting. Compensators also showed a preference for high-fat sweet food compared with non-compensators (NC), independent of the exercise intervention. Exercise-induced changes in the hedonic response to food could be an important consideration in the efficacy of using exercise as a means to lose weight. An enhanced implicit wanting for food after exercise may help to explain why some people overcompensate during acute eating episodes. Some individuals could be resistant to the beneficial effects of exercise due to a predisposition to compensate for exercise-induced energy expenditure as a result of implicit changes in food preferences.
Bottom line, SOME folks compensate, others do not. And those that do seem to do so more from a psychological drive than a physiological one. Now it's fair to say that it doesn't really matter why one might compensate by eating more if you do, but it is also fair to point out that this effect is far from universal.
The same commenter on Gary Taubes blog posted a second supposed "gotcha" study:
Nonprescribed physical activity energy expenditure is maintained with structured exercise and implicates a compensatory increase in energy intake
This study took middle aged sedentary men and prescribed an exercise program for 6 months or no exercise. There was no dietary intervention. They tested energy expenditure during exercise and the rest of the time at 2, 9 and 18 weeks and 2 weeks after "detraining" at study end. What they found was:
The adoption of regular structured exercise in previously sedentary, middle-aged, and overweight men does not result in a negative compensatory reduction in nonprescribed physical activity.
Yes, the weight loss wasn't phenomenal (1.8 kg +/- 2.2), but they did lose some weight. That's almost 4 pounds in six months. Not ground breaking, but the type of stuff that can prevent that sloooooow gaining in middle age.
What they also found was less than predicted (by caloric expenditure) weight loss:
The less-than-predicted weight loss is likely to reflect a compensatory increase in energy intake in response to a perceived state of relative energy insufficiency.
It is unfortunate that they didn't do any direct dietary assessment here. Self-reported diaries are not the best, but at least that might have shown if diet was really altered. Instead they did a calculation and estimated that the exercisers consumed around 100 cal/day more on average. They measured energy expenditure by "synchronized accelerometry and heart rate" (sounds like those Buggs used on TBL) so it is quite possible that this is in error.
Still, I believe this goes to what Dr. Oz was saying (and has certainly been my experience in maintenance) that if they ate 100 cal more a day, that's not an insignificant cushion to give a person a bit more room to enjoy a treat here and there. That's a slice of toast with a pat of butter for the low fatties or just a mouthful of butter for the low carber .
I've previously blogged on and frequently mention this study: Effects of aerobic exercise and dietary carbohydrate on energy expenditure and body composition during weight reduction in obese women
We can now add this study to the growing list of those demonstrating that we don't all become lazy slobs the rest of the day to compensate for our increased activity through exercising: Effects of exercise training amount on physical activity energy expenditure.
Oz was right in this segment. Taubes is just wrong.