I came across a very interesting article in the Ottawa Citizen this weekend, unpleasantly titled "For Canada's obese, exercise alone isn't going to cut it". The crux of the article is this - exercise will not help you lose weight. Every few months it seems that this issue pops up, including a cover article in TIME magazine last year, which Peter has previously dissected. This is a complicated issue, and given the sensational title, I wasn't expecting much from the Citizen article. But the article is actually very well written, and includes interviews with a number of excellent researchers (including Bob Ross, who supervised my MSc, and Tim Church, who has co-authored papers with both Peter and I), as well as physician Yoni Freedhoff of Weighty Matters. Since this issue comes up so frequently, and because of its public health importance, I thought this would be an excellent opportunity to "weigh in" with my opinion.
So, does exercise reduce body weight? To be completely honest, it depends on the situation.
Efficacy vs Effectiveness
In the Citizen article, they explain that some studies have found that exercise dramatically reduces body weight, while other studies have found it to have little to no impact. Why the discrepancy? It really boils down to study design. Some studies examine what exercise can do in an ideal situation. This is known as an efficacy study, and is the type of research that has been performed by Dr Bob Ross, with whom Peter is currently completing his PhD. For example, in one well-known study Dr Ross had a group of obese men walk or jog on a treadmill everyday for 3 months. The daily exercise session burned 700 calories, and diet was strictly controlled so that caloric intake neither went up nor down during the intervention. What happened? At the end of the 3 months, the participants lost an average of 7.5 kg (~16.5 lbs), through exercise alone!
This and other similar studies in women and the elderly have clearly shown that exercise alone can reduce body weight, especially when caloric intake is held constant. But it should be noted that participants in these studies are closely followed, with participants taking detailed diet records to make sure that caloric intake neither increases nor decreases, while every exercise session is strictly monitored by study staff. In other words, these participants represent a best case scenario, and a lot of time and effort goes into ensuring that they strictly follow both their nutritional and exercise plans.
Now of course the vast majority of people don't have trained staff following their every move. This is where effectiveness studies come into play. Instead of looking at the ideal situation, effectiveness studies look at what happens in everyday life. And in these studies, exercise often has a much more modest impact on body weight. For example, a very large study performed by Dr Tim Church and colleagues examined the impact of 6 months of aerobic exercise in obese, post-menopausal women. The women were randomized to three separate conditions - one group expended 4 calories/kg/week, one group expended 8calories/kg/week, and the final group expended 12 calories/kg/week. None of the groups were told to change their diet in any way. What happened? Surprisingly, all three groups lost about the same amount of weight - roughly 5 lbs. What's more, the weight loss was no different from control subjects who didn't exercise at all! How did this happen? Dr Church offers his best guess in the Citizen article:
"I think it was because they were rewarding themselves," says lead author Dr. Timothy Church, a medical doctor and professor of preventive medicine at Pennington Biomedical Research Center at Louisiana State University. "That's what we heard anecdotally: 'Man, I've made all my sessions this week. The wheels are off, I'm going to have a big dinner."
This is more like the situation that people commonly experience. If they are exercising without worrying about their diet, they may lose a few pounds, but probably not as much as they'd like. But is that really the end of the world?
The most interesting findings of both of the studies that I've discussed so far today is what happens in response to long-term exercise in the absence of weight loss. For example, in the above-mentioned study by Dr Ross, he had another group of men expend 700 calories per day through aerobic exercise, but he had those same men increase their caloric intake by 700 kcal/day, so that they experienced no change in body weight. Even though body weight remained unchanged, these men experienced significant reductions in visceral fat, which is a very strong predictor of diabetes, cardiovascular disease, and even mortality. Similarly, even though Dr Church reported no change in body weight following 6 months of aerobic exercise, the women still showed significant improvements in aerobic fitness, waist circumference, and fasting glucose.
And this is why this whole issue of exercise and weight loss is a bit of a distraction. Research has consistently shown that physical activity is associated with a lower risk of mortality, regardless of body weight. And both of the studies that I have discussed today have shown that exercise can result in important health benefits even when there is little or no weight loss taking place. When weight loss (or weight maintenance) is the goal, exercise still has an important role, but obviously so does diet. And even without weight loss, exercise is associated with tremendous health benefits. Can we all accept these simple facts, and avoid the sensational headlines for a few months?
Travis Saunders
UPDATE: An excellent letter to the editor from Dr Mark Tremblay explaining why neither diet nor exercise trumps the other when it comes to health, and why we should move past our fixation with body weight.
Church, T., Earnest, C., Skinner, J., & Blair, S. (2007). Effects of Different Doses of Physical Activity on Cardiorespiratory Fitness Among Sedentary, Overweight or Obese Postmenopausal Women With Elevated Blood Pressure: A Randomized Controlled Trial JAMA: The Journal of the American Medical Association, 297 (19), 2081-2091 DOI: 10.1001/jama.297.19.2081
Ross R, Dagnone D, Jones PJ, Smith H, Paddags A, Hudson R, & Janssen I (2000). Reduction in obesity and related comorbid conditions after diet-induced weight loss or exercise-induced weight loss in men. A randomized, controlled trial. Annals of internal medicine, 133 (2), 92-103 PMID: 10896648
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Good point about exercise and weight loss, people need to stop thinking that BMI is the be all and end all. It might be informative at a population level, but when it comes to individuals it is only one of several factors that need to be taken into account.
Do you know if there has been any research done into the negative impact of calorie restriction diets on exercise levels among people starting on combined weight loss and fitness programs? I always find that if I'm hungry (usually because I've been delayed at work) I can't seem to put the same effort into a workout, and end up doing less work overall. It strikes me that this might be one (of many) reasons why many diets do more harm than good.
@ Dave,
Thanks for not only noticing the problem, but giving us the advice needed to fix it! Very much appreciated.
@ Paul,
I'm not aware of any research looking at caloric restriction and exercise per se, but I wouldn't be shocked to know that CR reduced exercise performance, as well as non-exercise physical activity (e.g. taking the stairs vs the elevator, and even things like fidgeting). I often feel sluggish in my workouts if I've gone too long without eating, and it makes sense that caloric restriction would do the same. If I come across anything on the topic I will be sure to let you know.
Travis
"people need to stop thinking that BMI is the be all and end all."
People need to stop telling people that BMI is the be all and end all, through mainstream media, art, doctors that inform larger patients about exercise programs without first checking whether they exercise already, and hateful comments from the general public.
I think it's pretty well established that the combo (lifestyle intervention) works better than the components (diet and exercise) alone.
Hey Travis,
You and I have chatted about this many times and we probably don't need a rehash.
Today though I've got to ask, how exactly is the headline sensational? Exercise alone isn't going to cut it for folks trying to lose weight.
Given what I do for a living I get to meet a great many folks and talk to them about their weight loss efforts. An enormous percentage of them have undertaken exclusively exercise based approaches. Sharon's article does a great job of explaining why exercise alone ain't going to do it and I would argue reflects truth and not sensationalism.
Yoni
Ok, I've read the article you linked, and I saw the Time article when it came out. The recurring theme that I see is an underestimation of what constitutes "exercise". One of the studies touted 180 minutes per week. Sounds like a lot, until you realize that's just 25 minutes per day. I don't know how much exercise is required to expend 12 cal/Kg/wk, but I'm guessing it's only a little more. Declaring 20-30 minutes per day ineffective for weight loss is analagous to declaring 2500 calories/day an ineffective weight-loss diet. Our collective perceptions about the norms for exercise are as skewed as the supersized fast-food meals that became the norm in the late 90's.
Not to mention our perceptions of exercise intensity.
I am curious as to how to study these effects in general populations. I'd love to understand what are the real drivers of obesity in the general population; the experiments tell me I have written off exercise too quickly but I wonder what is the underlying causal mechanism of increased obesity? Is it a decline in physical activity?
In general I think that the conclusion "exercise won't help you lose weight" is largely true, but it's such an inherently misleading statement that it requires qualification.
1. Exercise by itself simply isn't going to burn many calories unless you make it an all-day affair. Most people don't have the time, let alone the inclination or motivation, to exercise that much. Sure, a competitive athlete without a full-time job and a family can burn up a few thousand kcal per day, but the average sedentary Joe? Not so much.
2. To most people, "exercise" connotes "go run". That complete ignores the role of exercise intensity in driving adaptations, including fat oxidation and calorie partitioning. If you're just going out to jog the same route at the same pace for a half hour a day, you'll see results if you're untrained, yes - but you're also going to hit a plateau sooner or later without further stimulus to drive further adaptation.
3. Exercising without a proper diet most certainly isn't going to help you, because left to him/herself, the average person eating ad-libitum is going to eat far too much for his/her activity level. That's why people are getting fat in the first place.
If you go out for an hour of exercise and burn a few hundred calories, but you come home starving and eat an extra 1000 kcal of food, then of course you're not going to get results. Diet and exercise have to go hand in hand.
Ultimately the headline is both right and wrong, depending on the context. I disagree with it mainly because it sends the wrong message; these days people are more interested in finding excuses for being fat so they can absolve themselves of responsibility. Telling people that "exercise won't help you" is the wrong approach, IMO.
@9 Matt, A couple of your points are illustrative:
"Most people don't have the time, let alone the inclination or motivation, to exercise that much. Sure, a competitive athlete without a full-time job and a family can burn up a few thousand kcal per day, but the average sedentary Joe? Not so much."
Yes, it's time-consuming, and given the (American) social values of "getting ahead" and working long hours, time is precious. But you don't need to burn "a few thousand kcal per day." 500 per day (an hour of *vigorous* exercise) results in a pound lost per week, if diet is kept unchanged.
"2. To most people, exercise connotes go run." I think a big part of the problem (as you suggest in the rest of that paragraph) is that for too many people, exercise connotes go *walk*, at least judging by the ratio of walkers to runners at my local park. Here is just one site showing energy expenditure by exercise:
http://www.mayoclinic.com/health/exercise/SM00109
Walking burns a pretty meager 180-270 kcal/hr, compared to 980 for running a 7:30 pace for an hour, 700 for jumping rope, 500 for swimming laps. To get to 500 kcals/day (to lose a pound a week) you'd have to walk 2-3 hours per day! Yet too many people walk 30-45 minutes and wonder why exercise doesn't work.
Your third point is self evident, although one could equally say "the average person eating ad-libitum is not going to exercise enough for his/her eating level.
I love this blog and I promiss to never post from my iphone again (please excuse any typos). Nordic skiing must be magic because I got back on my horse this winter and lost 30lbs. But now ski season is ending and I think I am going to cry. Anyone know anyother magic workouts?
@ Yoni,
I agree with you that the article itself does a very nice job of presenting the issues. But to me, the title ("For Canada's obese, exercise alone isn't going to cut it") seems to suggest that exercise is useless. Period. Whereas we know that exercise, in the absence of any change in diet or weight loss, still has a lot of great health benefits. So that was my only concern with the title.
Do you have a sense of why your patients would choose to focus on exercise alone, rather than exercise and diet in combination? Is it because focusing on exercise seems more pleasant than changing their diet?
@ SurgPA
I'm sympathetic to your point that these studies don't always involve a huge volume of exercise, but I think this is one of the issues that Yoni brought up in the article - like it or not, most people are not willing/able to burn 500 calories through a single bout of exercise. For those of us brought up in the traditional exercise physiology world (which focuses mainly on athletes and athletic performance) it doesn't seem like a big deal at all. But it's an unrealistic goal for many inactive individuals, especially early in their exercise program. Now of course it may be possible to expend 500 calories throughout the course of the day by increasing Non Exercise Activity Thermogenesis (e.g. taking the stairs instead of the elevator, and other small but important changes) and decreasing the amount of time spent sitting. This is the area that I'm most interested in personally.
Travis
Bullocks. It's not an "all-day affair." If a run takes an hour, then including getting ready for the run, stretching, and showering when you're done must take 5-6 hours to be a "all-day affair."
You can easily burn 300-700 calories in a single hour jogging or running.
Most people could find *more* than an hour per day to go for a run and burn 400-700 calories easily (depending on their pace).
Don't have the time, inclination or motivation? I think what you're looking for here is "most people would rather watch TV."
Travis,
I agree that real-world experience shows most people are not willing/able to do sufficient exercise, but couldn't that same argument be made about the necessary dietary changes? Ultimately weight loss is about behavioral change; an individual needs to alter the behaviors that lead to his/her current weight. Durable behavior change is difficult to achieve, whether it's dietary change or activity change; it comes back to your earlier point about efficacy vs effectiveness. I would argue that a proper exercise trial is equally efficacious to a proper dietary trial, but that so far neither has been shown to be terribly effective *in the long term,* ie longer than 2-3 years.
I'd be interested to hear more about your ideas/results with non-exercise activity thermogenesis. The caloric math makes sense; the 250 calorie donut-a-day - "what's one donut?" - from the lunch cart at work adds 18 pounds per year, (250x5x52/3500=18.5)so a 250 calorie change in behavior should have the reciprocal effect. But does it really work?
@ Backpacker - Have you tried roller skiing? It's the dryland equivalent of nordic.
Travis I think it's twofold.
Firstly people prefer exercise because they enjoy it more than changing dietary choices.
Secondly people believe wholeheartedly that exercise is responsible for the lion's share of weight and part of that belief frankly comes from the constant in your face opinions of the media, public health agencies, bloggers etc. that seem to point to that same conclusion.
@ SurgPA,
James Levine has done a few studies suggesting that NEAT could play a large role in weight management, but it's such a new area that I don't think anyone can say for sure. I've summarized his work in a guest post I did last fall on Summer Tomato. One problem with NEAT is that it's very tough to quantify, so most new papers seem to be focusing more on sedentary time (e.g. sitting), which is sort of (but not exactly) the opposite of NEAT, and much easier to measure.
While NEAT/sedentary behaviour may well play a role in weight management, some of the most interesting mechanisms linking them with health may have little or nothing to do with body weight. So like exercise, there may be some very good reasons to increase NEAT/decrease sedentary time regardless of your body weight, and even regardless of the amount of exercise you perform on a daily basis. I did a post on this a few weeks ago on our old site, and will try to do another in the near future here.
So to answer your question - I'm not really sure at this point, but it's an incredibly interesting area of study.
Travis
" But now ski season is ending and I think I am going to cry. Anyone know anyother magic workouts?
Posted by: the backpacker | March 9, 2010 10:15 PM"
That's great that skiing works so well for you. For some fun exercises, Ross Training (rosstraining.com) has some good suggestions.
Some people like stuff like crossfit, too. The MMA site, "sherdog" (sherdog dot net) has a "Conditioning sub forum" that has a challenge of the month exercise. cool suggestions are there, too.
You can even get x-country skis with little wheels on them to go on pavement.
good luck to you !
I added an update to the original post, but thought I'd include it as a comment as well:
The Citizen has published an excellent letter to the editor from Dr Mark Tremblay explaining why neither diet nor exercise trumps the other when it comes to health, and why we should move past our fixation with body weight.
You can read it here.
@13
400-700 calories is not a significant calorie burn if:
1) you're already eating >1000 kcal more than you need (many, maybe even most, are)
and/or
2) your diet doesn't remain unchanged (most will eat more to compensate for being hungry from exercise)
Sure, it sounds simple - go burn an extra 500 kcal/day and the weight will just fall off. In practice? Adipostatic regulation is a bitch.
@19 - Matt, Actually, 400-700 calories *is* significant, even if you're eating 1000 excess kcal. At 500 kcal of exercise, that reduces weight gain from 2#/wk to 1#/wk. I think your point is that dramatic overeating is difficult to counter through exercise, to which I'd agree.
Your second point may get to the heart of the matter. I'm not convinced most people overeat because of true hunger. I certainly don't most of the time. I suspect a lot of overeating comes from social cues (it's noon, so it much be time for lunch)and from the instant gratification from enjoying the texture and flavor of food. Afterall, how many people binge on celery and brussel sprouts - no offense intended to the sproutophiles reading this? The foods I would point to in my own experience are the "pleasure foods"; cookies/ muffins/sweetbreads, etc.. When people get done with a workout and binge on sweets, I don't believe it's truly from hunger (particularly for the 30-45 minute low-intensity workout burning a paucity of available glucose and glycogen.) I suspect, without any data, it's more of a pleasure-reward for good behavior.
I know of roller skis. They are fun but cost alot. Thanks for the leads on workouts my goal is cut cut my times by ten percent next year so dry land is a must. Off topic does any one know the effect of working out in the cold? It always seems that I burn off pounds alot faster during the season then in the summer even doing hill workouts and biking alot (in my younger years).
Over on another thread, Peter pasted this awesome workout:
25 body weight pull-ups (can use assisted if necessary)
50 deadlifts @ 135lbs or whatever weight is doable (your favourite!)
50 regular pushups
50 box jumps (about knee height - can use a bench if needed)
50 floor wipers (tough to explain - may need to google or youtube this one - primarily ab exercise)
50 single arm dumbbell clean/press @ 35lbs (25 per arm)
25 body weight pull-ups
wanna build up to this!
That's an interesting point you bring up. It's a fact that most people who need to shed a pounds probably don't get enough exercise. But for the people that do hit the gym on a regular basis, I think it's more that you can't out train a bad diet. The two have to go hand in hand to produce the maximum effect.
And BTW...VikingMoose's exercise routine is a killer! I printed it off to take to the gym with me this week. NICE!
Your second point may get to the heart of the matter. I'm not convinced most people overeat because of true hunger. I certainly don't most of the time. I suspect a lot of overeating comes from social cues (it's noon, so it much be time for lunch)and from the instant gratification from enjoying the texture and flavor of food. Afterall, how many people binge on celery and brussel sprouts - no offense intended to the sproutophiles reading this? The foods I would point to in my own experience are the "pleasure foods"; cookies/ muffins/sweetbreads, etc.. When people get done with a workout and binge on sweets, I don't believe it's truly from hunger (particularly for the 30-45 minute low-intensity workout burning a paucity of available glucose and glycogen.) I suspect, without any data, it's more of a pleasure-reward for good behavior.