Thursday, November 1, 2007

Exercise for weight loss doesn't work?

There has been a bit of a debate recently on some blogs prompted by some comments within Gary Taubes new book: Good Calories, Bad Calories. The book is an excellent survey of the scientific research regarding diet and fat loss. One of the things he looks at is how the studies show that exercise is pretty ineffective for making people lose weight. exercising to stay healthy is one thing, but exercising to lose weight is usually doomed to failure.

This is another argument that seems somewhat heretical but Rob Wolf - a very good strength & conditioning coach (and former research biochemist - so he knows his science) - pointed out in a recent blog post that in his experience of training people over a number of years it is only when people adopt a fairly low carb diet that they make a significant change to their body composition.

Our nutritional recommendations are focused at insulin control. You could also say that our nutritional recommendations are what we are designed to eat and thrive on…but that sounds all hoity-toity. I wish soooo much that simply crushing people during a workout would solve the fat and body comp problem however, it simply does not. There are 168hrss in the week. We can crush folks for 3 of those hours and then they can destroy themselves with bad food choices for the remaining 165hrs. From what we see in the literature and day to day experience, we could exercise people morning, noon and night and if the food composition is poor they will pack in enough insulin spiking food to maintain or even regress. It’s a bummer, but it’s true.

This was also discussed a bit on Art DeVany's blog, although he concludes by saying that the food/activity set cannot be differentiated too easily:

Think of what happens to a hunter-gatherer when they leave the traditional life and go to the city. Both their activity and their diets change. They quickly become diabetic or pre-diabetic, whether they are Australian aboriginals or Eskimo. In the bush or wild their diets differ dramatically, though their activities are equally demanding. Yet, they share the same fate when they leave the bush for the city. They exchanged their evolutionarily adapted way of life for something very different. And, both suffer similarly. When they go back into the bush or tundra, they recover their health and strength. Which is the more important change? Their food or their activity? There is no answer because they are intertwined in metabolic networks and gene interactions that are far too complex to separate or assign degrees of "importance" to.

Anyway, I do not want only to be pointing to other blogs. I thought that this news story supported Taubes and Wolf:

There is no "one size fits all" when it comes to weight loss through exercise, says Queensland University of Technology behavioural scientist Neil King.

Dr Neil King, from QUT's Institute of Health and Biomedical Innovation, is the lead author of a study conducted in collaboration with the University of Leeds in the UK, which has been published in the latest edition of the International Journal of Obesity.

"When it comes to losing weight, a lot of people assume if you lose less than the predicted weight then you aren't exercising enough, and that is why you aren't getting the desired results," Dr King said.

"This study is the first evidence-based study that shows despite people doing the same amount of supervised exercise people lose different amounts of weight."

The study, which focused on 35 overweight and obese people from the UK, sought to identify and characterise the variability in exercise-induced weight loss.

Participants undertook a 12-week supervised exercise program that was individually tailored to expend 500 calories per session. During this time their weight loss and behavioural outcomes were monitored.

Dr King said the study found the role of exercise as an effective weight management method could be undermined by "compensatory responses" such as a person's increased hunger and food intake as a result of their increased energy expenditure.

"People, who we refer to as compensators, are those who compensate for the increase in exercise-induced energy expenditure, by adjusting their food intake" he said.

"For some people this might be in responses to an automatic biological drive, whereas for others it might be a deliberate reward-based increase."

Dr King said what this study showed was that some individuals were predisposed to compensatory responses, rendering them resistant to the theoretical weight loss benefits of exercise.

"The individual variability here demonstrates the need to treat people as individuals," he said.

"It also highlights the importance of determining the mechanisms that may explain this variability, such as how to treat the more resistant compensatory person to improve their weight management outcomes.

"Those resistant to exercise might be better suited to weight management strategies which include controlled dietary intake, in addition to exercise."

Dr King said the novelty and therefore the strength of this study, was that the exercise was supervised.

"Therefore, unlike unsupervised exercise interventions, any variability in weight loss cannot be explained by differences in exercise compliance," he said.
There is another study here by the same scientists that says basically the same thing: some individuals will be predisposed to compensatory responses that render them resistant to the weight loss benefits theoretically associated with an exercise-induced increase in energy expenditure.

Taubes, Wolf and DeVany of course would tell us that the key issue that King needs to take account of is insulin control....which means a lower carb diet or some fasting.


Anonymous said...

Meaningless twaddle. The report you cite just says that each person exercised to expend 500 calories per session. But what were they doing? Walking on a treadmill while reading a magazine? Or did the exercise include resistance training and interval workouts? Not all workouts are the same and without that specific info, this is study shows nothing.

Chris said...

Twaddle? Maybe, but I am only pointing out the research. If you read the rest of this blog you'll have seen that I often promote interval training. In the Rob Wolf post I pointed to he does make the point that intervals may prove more effective. Plus, exercise increases insulin sensitivity so there may be more to look into there.

However, when most people try to exercise to lose weight they do not do intervals - they walk 10,000 steps a day or jog or swim or whatever - standard "cardio", so while your point is valid it is not necessarily relevant to what most people do.

Did you read the Taubes article that I linked to in the NY Times?

Chris said...

There is more on this subject from Rob Wolf on Art DeVany's blog, with some before and after shots :