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Burning calories without stimulating appetite

April 19th, 2010

I’ve posted a few times recently on the challenges of losing weight — in particular, the homeostatic mechanisms that your body uses to fight against any attempt to burn more calories than you consume. For instance, exercising stimulates appetite hormones that prompt you to eat more. So I found the following tidbit in the New York Times interesting:

In a completed but unpublished study conducted in his energy-metabolism lab, [Barry] Braun [of UMass-Amherst] and his colleagues had a group of volunteers spend an entire day sitting. If they needed to visit the bathroom or any other location, they spun over in a wheelchair. Meanwhile, in a second session, the same volunteers stood all day, “not doing anything in particular,” Braun says, “just standing.” The difference in energy expenditure was remarkable, representing “hundreds of calories,” Braun says, but with no increase among the upright in their blood levels of ghrelin or other appetite hormones. Standing, for both men and women, burned multiple calories but did not ignite hunger. One thing is going to become clear in the coming years, Braun says: if you want to lose weight, you don’t necessarily have to go for a long run. “Just get rid of your chair.”

This suggest that all those people trying to work at “stand-up” desks may be onto something. On the other hand, I’m still not completely sold on the general message about exercise and weight loss that is more or less accepted as fact in this article:

“In general, exercise by itself is pretty useless for weight loss,” says Eric Ravussin, a professor at the Pennington Biomedical Research Center in Baton Rouge, La., and an expert on weight loss.

The article then describes one of Ravussin’s studies (which I blogged about back in December) in which one group of subjects lost nearly 10% of their bodyweight, or a pound a week, through exercise alone — which seems to contradict the assertion that exercise is useless for weight loss.

But in the exercising group, the dose of exercise required was nearly an hour a day of moderate-intensity activity, what the federal government currently recommends for weight loss but “a lot more than what many people would be able or willing to do,” Ravussin says.

Oh, now I get it. It’s not that exercise is useless for weight loss — it’s doing a little bit of exercise at a low intensity that is useless. Those are two very different statements. I understand that an hour a day of moderate-intensity exercise is a tall order for people in today’s busy, convenience-driven, nutritionally bankrupt society etc. etc. But that doesn’t mean exercise is useless, it just means that it takes a lot of exercise — more, perhaps, than most people are willing to do — to see appreciable changes.

  1. Peter Chapman
    April 19th, 2010 at 01:14 | #1

    Hi Alex, If standing burns more calories than sitting, what about people (like me) who sit on an exercise ball at their office job? How does sitting on the ball compare to sitting or standing? Peter

  2. alex
    April 19th, 2010 at 05:06 | #2

    @Peter Chapman Interesting question, Peter — so interesting, in fact, that I’ve made the answer into a separate post!

  3. Sarah Lozie
    April 28th, 2010 at 19:03 | #3

    I think when we’re looking at weight loss, we have to take into account the physiology behind your body getting the energy it needs to fuel the exercise. A common misunderstanding is that “the harder I work out, the more fat I’ll burn!” when in actual fact, high intensity exercise takes its energy from muscle and liver glycogen and hardly touches your fat stores. Do people understand that to shed excess fat, walking may very well be the best prescription?? Counterintuitive, but it gives your body the chance to oxidize your fat stores and burn them up, while sparing your glycogen. Amazing! Also prevents post-work-out ravenous hunger to replenish those glycogen stores and then some….
    So, doing a little bit of exercise at a low intensity may be useless, but doing A LOT (>1 hr/day) of exercise at a low intensity is by far the best way to lose weight.
    Would you agree?
    Sarah

  4. alex
    April 28th, 2010 at 20:52 | #4

    @Sarah Lozie
    Thanks for the comments, Sarah. To be honest, I don’t really agree. I’ve posted a couple of times about the “fat-burning zone” and idea that low-intensity exercise is best.

    This post (http://sweatscience.com/?p=545) talks about a study that came out a few months ago suggesting that if you burn more fat, the body simply converts spared glycogen into fat for storage. All that really matters is your total caloric deficit (or surplus).

    This post (http://sweatscience.com/?p=615) does the math on low-intensity versus moderate intensity exercise for fat burning. The basic point: If you go for a leisurely walk and burn 100 calories, it’s true that 85 of them will be provided by fat. But it’s a lot better to go for a moderate run and burn 500 calories in the same amount of time, with 250 from fat. Especially since, for most people, time is the main limiting factor that prevents them from exercising more. If you have time to walk for three hours a day, then that’s great. But if you’re trying to fit your exercise into an hour a day, more intensity will help you.

    Obviously weight loss is extremely complicated, and you have to consider other factors like appetite stimulation (and, more generally, diet). I’m not saying it’s simple or easy — but I don’t think the advantages of burning a higher percentage of fat by taking it easy outweigh the benefits of burning triple the number of calories overall by going harder.

  5. Sarah Lozie
    April 29th, 2010 at 13:35 | #5

    Thank you for your thoughts, I’ll look into the posts. What I wanted to highlight though, is the tendency to overeat following an intense workout. That seems to be one of the perpetual factors in the ‘struggle’ to lose weight. Moderate exercise will not mentally stimulate the appetite as greatly as intense exercise.

  1. April 19th, 2010 at 05:05 | #1