Archive for the ‘Health Promotion’ Category
From a certain point of view (as Obi-Wan Kenobi might say), John Cloud’s article in TIME Magazine, “Why Exercise Won’t Make You Thin” is understandable. The man is a working writer who’s success is based on being dependable – being able to turn out a product of predictable quality and being able to stick to a schedule. That, from a certain point of view, his article resembles little more than a loosely fact-checked blog post, is more the responsibility of TIME’s editors. However, it would be too easy to chalk this article up to poor-quality writing and editing – far from it. Instead, I would argue that “Why Exercise Won’t Make You Thin” was precisely what TIME was looking for because it contained a message that resonates with a substantial potion of its readership; that message being “it’s not your fault that you’re overweight – exercise and self-control don’t work, and science has proved that”.
Cloud shows some surprise that exercise, at least the way he appears to define it, doesn’t fully offset the calories you take in, particularly if you’re trying to lose weight,
You might think half a muffin over an entire day wouldn’t matter much, particularly if you exercise regularly. After all, doesn’t exercise turn fat to muscle, and doesn’t muscle process excess calories more efficiently than fat does?
That last statement, in Cloud’s hands, becomes a strawman to be knocked down and so there is no exploration of how diet, exercise, muscle and fat are interrelated. No, exercise doesn’t turn fat into muscle. However, aerobic exercise in combination with a mild calorie deficit will burn fat. This combination by itself will also burn some muscle, so some strength training should accompany it to help you hold on to as much of your muscle mass as possible, while the fat burning is under way.
We now return to TIME:
Yes, although the muscle-fat relationship is often misunderstood. According to calculations published in the journal Obesity Research by a Columbia University team in 2001, a pound of muscle burns approximately six calories a day in a resting body, compared with the two calories that a pound of fat burns. Which means that after you work out hard enough to convert, say, 10 lb. of fat to muscle — a major achievement — you would be able to eat only an extra 40 calories per day, about the amount in a teaspoon of butter, before beginning to gain weight. Good luck with that.
Checking out this article, which is a review of the various methods for calculating resting energy expenditure (REE), does reveal as part of a conceptual model for REE that internal organs such as heart, kidneys, liver and brain have higher resting metabolic rates compared with skeletal muscle (13 kcal/kg-day) and body fat (4.5 kcal/kg-day). Checking the math indeed shows this to correspond to 6 kcal/day and 2 kcal/day (kcal = the “calorie” we hear about). However, for purposes of fat loss (hence weight loss), what we’re interested in is total energy expenditure which in the introduction to this article is described as the sum of five components: REE, physical activity-induced energy expenditure, thermic effect of food, facultative thermogenesis (energy expenditure in response to hot or cold conditions – sweating or shivering) and anabolism/growth. It’s the physical activity and the anabolism (muscle growth induced by strength training) that’s going to promote weight loss.
In the end, I can only say that John Cloud’s experience with weight loss seems to be completely different from mine. When I’m working on weight and fat loss (which isn’t continually), the strategy has been mild calorie reduction, food selections based on calculated macronutrient ratios (say 35%/35%/30% protein/carbs/fats) with a bias towards lean protein, vegetables, fruit, low glycemic index carbs, healthy fats such as fish and olive oil, combined with exercise intensity and duration along the American College of Sports Medicine recommendations (at least 150 minutes per week), mixing different modes of cardio with strength training including weight lifting. I can attest that this strategy has worked for me, allowing me to lose 50 lbs, keep it off for over eight years, and put me in striking distance of seeing my abs again. There are time sacrifices involved (you have to do some shopping and cooking), and I need to accommodate this within the schedule associated with being a success-addled corporate professional. However, I don’t regret one bit making fitness a goal in my life. I’m even starting to enjoy working out. One other thing I can recommend to John, beyond doing some weight training and paying closer attention to diet is to find a workout partner. Maybe his next article on exercise, fitness and diet might actually be informing and inspiring.
Disclosure statement: I’m a gym rat and I’m married to a fitness writer. My wife drew me into the fitness habit several years ago. In the intervening years I’ve gone from borderline obese, losing nearly 50 pounds and reducing my body fat several percent, to nearly normal body composition. This was accomplished primarily through a combination of diet, strength training and cardiovascular exercise. My perception of working out has evolved from a grim “something I have to do to keep from dying early” to something I’m getting a little bit of a kick out of.
Thus explains my barely concealed annoyance with John Cloud’s article in TIME Magazine, “Why Exercise Won’t Make You Thin”. Beyond the sweeping pronouncement that “exercise doesn’t work” because he can’t see any progress, there’s a deeper story in how scientific information is used to inform people on a policy issue – in this case, the role of diet and exercise in promoting wellness. Media outlets report on issues using drama and narrative structure, casting the participants in an event in terms of heroes and villains, for the sake of readability. However, the real world is complicated, and such a narrative structure can mislead readers by depicting events as having clear cause-and-effect relationships, when the real circumstances are not at all clear. When combined with the tendency to reinforce the status quo and to appeal to fairness (i.e. presenting both “sides” of an issue, regardless of how wrong one side might be), this thwarts the introduction of scientific thought into public discourse. In this case, the result is an article in a major media outlet that misinforms readers about the role and effectiveness of exercise in achieving and maintaining a healthy body composition.
John introduces the story with his workout experience, highlighted with the plaintive cry about why isn’t it making his gut go away. He observes that, “. . . like many other people, I get hungry after I exercise, so I often eat more on the days I work out than on the days I don’t,” and wonders if exercise could be keeping him from losing weight. I have to ask, what’s he eating after he exercises?
His thesis then is:
The basic problem is that while it’s true that exercise burns calories and that you must burn calories to lose weight, exercise has another effect: it can stimulate hunger. That causes us to eat more, which in turn can negate the weight-loss benefits we just accrued. Exercise, in other words, isn’t necessarily helping us lose weight. It may even be making it harder.
The underlying science he introduces as evidence of his point is a paper published by the Pennington Biomedical Research Center at Louisiana State University. In this study, the investigators examined compensatory mechanisms resulting from exercise which reduced or offset weight loss. The study was performed with sedentary, overweight or obese post-menopausal women who performed different levels of exercise under controlled conditions. The women were assigned to one of three groups of energy expenditure, 4, 8 or 12 kcal/kg-week for six months. All participants started at the lowest level; with the ones assigned to the higher groups ramping up to their designated level over the first 4 to 8 weeks. Relative perception of exertion was recorded, but not discussed in the paper, so we don’t get any sense to how hard the women felt they were working.
The investigators seemed to have measured everything that could have mattered in an exercise study. Actual measured weight loss was compared with predicted weight loss; predicted weight loss was based on the assumption that expending 7,700 kcal corresponded to 1 kg of weight. The difference between measured weight loss and predicted weight loss is termed “compensation” and is an important metric in the study. Body fat changes were measured with skinfold tests. Changes in waist circumference also were measured. Participants’ diets were documented by questionnaires, but other than reporting energy intake, diet was not analyzed in this study.
The results from the study were that women in the low (4 kcal/kg-week) and moderate (8 kcal/kg-week) groups experienced weight loss comparable to predicted weight loss. The highest energy expenditure group (12 kcal/kg-week) experienced less weight loss than was predicted. In the investigators’ terms, compensation was occurring at the high group which attenuated weight loss. All groups showed reduced waist circumference, including the controls, and body fat was consistent across all groups, controls included. The results don’t point to a “smoking gun” for why compensation occurred. The investigators observe that the methodology for estimating food consumption was not optimal for measuring small changes in energy intake, which is not a trivial uncertainty in this study. In the end, they speculate based the work of others that increased energy intake is the source of the produced weight losses that were less than predicted. It wouldn’t take much, really: the highest energy expenditure group (12 kcal/kg-week) corresponds to about 1,020 kcal/week. The 1,020 kcal/week energy burn corresponds to 145 kcal/day or about half of a Starbucks blueberry muffin. The investigators noted that about one fourth of the high group didn’t exhibit compensation (in other words, they lost as much or more weight than predicted), suggesting that the higher levels of exercise work for some individuals. They point to the Weight Control Registry which demonstrates that individuals who have lost a substantial amount of weight and maintained that weight loss typically get in 45 minutes or more of moderate exercise per day. There appears to be those who are not prone to compensation, or “who have developed strategies to combat compensation”. Such as being more thoughtful about what they eat while on a weight-loss program?
So what happens when this hits the mainstream media?
“’In general, for weight loss, exercise is pretty useless,’” says Eric Ravussin, chair in diabetes and metabolism at Louisiana State University and a prominent exercise researcher,” quoted by Cloud. However, a careful reading of the research paper cited at length in the TIME article, and produced by a colleague of Dr. Ravussin’s, doesn’t say that. The juxtaposition of that quote, without any other context, with a study cited as the “proof” (it isn’t really) misleads readers into thinking there is scientific evidence that “exercise doesn’t work”.
The findings were surprising. On average, the women in all the groups, even the control group, lost weight, but the women who exercised — sweating it out with a trainer several days a week for six months — did not lose significantly more weight than the control subjects did. (The control-group women may have lost weight because they were filling out those regular health forms, which may have prompted them to consume fewer doughnuts.) Some of the women in each of the four groups actually gained weight, some more than 10 lb. each.
First of all the control lost weight – an average of 0.9 kg (less than 2 pounds) over the course of six months. The investigators also observe that those control individuals who lost weight had lower energy intakes. The controls weren’t zero-exercise people either. Everyone in the study carried a step counter, and while the investigators didn’t explore this facet, it is likely that some of the control participants walked. The speculation that the control individuals reduced their energy intake because it was being monitored isn’t found in the paper. The most that the investigators say is that the food questionnaire has limitations, and that all the dietary results need to be interpreted with caution, which presumably applies to the exercise groups. Keep in mind that we’re talking about pretty mild exercise. These women pedaled recumbent bikes or walked leisurely on treadmills (they’re sedentary individuals, remember?). The exercise producing the highest energy expenditure corresponds to losing about a pound per month. The notion of the exercise groups “sweating it out with a trainer several days a week for six months” is laughable. While the imagery makes for a more vivid story, it distorts out of proportion what actually happened during the research. Finally, looking at the average weight losses out of context with all of the data further misleads readers. While there may have been no statistically significant differences in weight loss among the groups, controls included, examination of the frequency distributions seems to show that lower proportions of the exercise groups gained weight. Focusing only on the fact that some individuals gained weight is also misleading to readers. Nothing is mentioned in the TIME article about the investigators’ observations of individuals who might have developed strategies to overcome compensation.
This is enough for one day (there is other stuff to do, of course). But there is more to explore, such as the misleading stuff about the differences between muscle and fat, and the inappropriate use of the “self-control is like a muscle” metaphor. We’ll come back to this.