Jimmy Akin

A reader writes:

I agree that just because someone is overweight doesn’t necessarily mean they eat to much…however it does mean they don’t exercise

I’m sure that you probably don’t mean this to be taken as a technical statement, but . . . it’s . . . not . . . true. It comes across as a diss to people who are overweight. It sounds like a cavalier dismissal of their situation, including whatever efforts at exercise they may be making. It would be better to make the statement in a more qualified manner, for as it stands it is subject to a number of criticisms:

1) Exercise is not a binary phenomena. People don’t fall into two classes of “those who exercise” and “those who don’t exercise” with no further relevant distinctions. Physical activity is something that exists on a continuum, and merely falling into the “does exercise” category is not a guaranteed cure for the problem of overweight.

2) Even falling into the category of “does a lot of exercise” isn’t a guarantee of losing body fat. Look at professional football players. Those guys tend to get a lot of exercise, but they also tend to have a lot of body fat (because they consume more calories in order to simultaneously [a] keeping doing the exercise and [b] keep their bodies at the homeostatic weight points they want to remain at).

3) Depending on the metabolic state one is in, doing exercise can increase the appetite one has, as the body tries to stay at its homeostatic weight point and responds by increasing appetite as physical activity increases. If you just add some exercise without addressing dietary considerations, this is likely what will happen to you: You’ll just eat more. (Paradoxically, there are also states–which dieters can exploit–where the body decreases appetite as exercise increases. The point is simply that not everyone who exercises is going to lose weight.)

4) Even when one is in high weight loss mode, exercise is rarely if ever a sufficient condition for that weight loss. Exercise tends not to add that much to the calories we burn each day. Consider:

A 6’0″, 200 lb., 30 year old man is likely to have a Basal Metabolic Rate (BMR) of 2019 calories per day (BMR Calculator). This is the number of calories he needs just to lay in bed, without adding any physical activity. If you add his daily work duties to this (let’s say he does office work), you might get the number up to 2500 calories.

Let’s just stick with his BMR for the moment, though. How much physical activity would he need in order for exercise to equal what he needs to just keep the lights on and the machinery working? Well, he’d need to generate another 2019 of calorie burning through exercise. How much is that? It depends on the exercise he does, but let’s take a common one that is easily within the reach of almost all dieters: walking. If a person of his weight walks briskly for half an hour, he will burn approximately 220 calories. This means that in order for his exercise-based calories to equal his BMR-based calories, he would have to walk briskly for 4.6 hours a day. (NOTE: There are some quibbles to make with these numbers, but they don’t affect the scale of exercise required, so we can stick with these numbers for purposes of showing the principle.)

Very few people are able to make that kind of exercise investment, and so exercise rarely plays as big a role in calorie expenditure as BMR. The result is that diet rather than exercise tends to be the most important factor in weight loss. In order to effectively lose weight, dietary change is what is needed. Exercise is an important adjunct to this (otherwise I wouldn’t do five miles of aerobic power walking per day, plus weight training), but exercise by itself is not the solution to weight problems for most people. It’s not even the major factor. Diet is more important.

6) Exercise also is not a necessary condition for weight loss. A few years ago I was dealing with a significant weight problem and lost almost seventy pounds without doing any exercise, simply by making a dietary change.

Diet rather than exercise tends to be the dominant factor in weight loss. The trick is, how to take in less calories than you expend without being eaten alive by hunger–a subject I imagine we’ll end up discussing in the fullness of time.

MEMO TO THE BBC: Get the loading dock ready. There’s a big truckload of “Duh!” coming your way.

Don’t get me wrong, I’m always glad when stories appear in the press pointing out that obesity is not simply a product of gluttony. I just get annoyed when this is portrayed as a revolutionary new discovery. It isn’t. We’ve know it for a long time. It’s simply that the news media (of which the BBC news service is at least ostensibly a part) has not done an effective job communicating the fact. Instead of doing real investigative journalism into the subject, they have been content to pass off to the public the expostulations of countless diet and exercise quacks, including that people are obese because they simply and irresponsibly eat too much.

Wrong.

Eating more calories than the body requires is part of the obesity phenomenon, but the situation is way more complicated than that, and it isn’t hard to tell why. Let’s do a little math:

1) Suppose that a particular 20-year old person needs to consume 2500 calories a day given his metabolism and level of exercise. (This is not at all unreasonable. The “2000-calorie recommended daily intake” that you read about on food labels is–for some unexplained reason–based on the calories consumed by the average post-menopausal woman. It is not representative of what a younger person or a male person needs to eat.)

2) Now suppose that the person actually eats 10% too many calories, or an extra 250 calories per day. Know how much weight the person will gain in a year?

3) 250 calories x 365 days = 91,250 calories. Since there are about 3550 calories per pound of body fat, the person would gain 25.7 lbs. in the course of a year.

4) Now let’s suppose that we project the trend into the future. Suppose that the person continues to eat 250 too many calories per day for a decade. At the end of ten years, when the person is 30, he will have gained 257 lbs. and can be expected to weigh between 400 and 500 lbs.

Know very many 30-year old people who weigh between 400 and 500 lbs?

Didn’t think so.

Even people who give no attention at all to their caloric intake (such people being legion) do not usually gain 26 pounds a year or end up weighing between 400 and 500 pounds by the time they are thirty.

The only possible explanation for this is that the great majority of people–even overweight people–are not overeating more than 250 calories a day.

Now let’s flip the situation around:

5) Suppose that the same 20-year old person underate by 250 calories per day? How many pounds would he lose in a year? That’s right 25.7.

6) And what would happen in a decade? He’d be dead.

If he were magically able to continue losing weight evenly throughout the decade, he would have exhausted his entire body mass before the decade was up. In reality, though, unless you are The Incredible Shrinking Man, you can’t continue to lose body mass indefinitely. You’d probably die around the time you hit 70-90 lbs.

This means that people do not undereat by more than 250 calories per day, either.

Except for a the rare cases of a few individuals who starve themselves to death or who gain 250 pounds in a decade, most people consistently stay within an average of 250 calories of where the number they need to metabolize each day or within about 10% of the needed amount.

Further, even people who give no attention at all to their diet do this. The only conclusion is that there is a mechanism in the human body that pushes us to stay within that range of our needed caloric intake. (In actuality, the range is narrower than I have indicated, but I wanted to use simple obvious numbers to make the point.) Our bodies have a “weight regulator” fuction that works like a thermostat, keeping our caloric intake within a modest range of the number of calories we need per day.

From a phenomenological perspective, the tools the body uses to keep us in that range are feelings of hunger and satiety. When the body wants to jack up our calorie intake, it hits us with feelings of hunger. When it wants to tamp down our calorie intake, it hits us with feelings of satiety.

This means that the great majority of overweight people are not simply gluttonously sucking down food. If they were, their weight would quickly spiral out of control and keep going up until they died. Instead, they are simply eating when their body tells them to eat and not eating when it tells them to stop. In other words, they are responding to the biological imperative that is implanted in them.

Now, for obese people something has obviously gone wrong with the situation or they wouldn’t be overweight, but for most the problem is not the vice of gluttony. They are simply doing what their body is telling them to do.

I don’t have space in this blog entry to talk about what has gone wrong or how it can be fixed, but I’ll be happy to do so if folks want me to.

For now, we need to bear the above in mind when we are tempted to look down on people who are overweight–or who are more simply overweight than we are. Unless they’re experiencing rapid weight gain at the moment, they’re not eating beyond what their bodies are asking them to.

MEMO TO THE BBC: Get the loading dock ready. There’s a big truckload of “Duh!” coming your way.

Don’t get me wrong, I’m always glad when stories appear in the press pointing out that obesity is not simply a product of gluttony. I just get annoyed when this is portrayed as a revolutionary new discovery. It isn’t. We’ve know it for a long time. It’s simply that the news media (of which the BBC news service is at least ostensibly a part) has not done an effective job communicating the fact. Instead of doing real investigative journalism into the subject, they have been content to pass off to the public the expostulations of countless diet and exercise quacks, including that people are obese because they simply and irresponsibly eat too much.

Wrong.

Eating more calories than the body requires is part of the obesity phenomenon, but the situation is way more complicated than that, and it isn’t hard to tell why. Let’s do a little math:

1) Suppose that a particular 20-year old person needs to consume 2500 calories a day given his metabolism and level of exercise. (This is not at all unreasonable. The “2000-calorie recommended daily intake” that you read about on food labels is–for some unexplained reason–based on the calories consumed by the average post-menopausal woman. It is not representative of what a younger person or a male person needs to eat.)

2) Now suppose that the person actually eats 10% too many calories, or an extra 250 calories per day. Know how much weight the person will gain in a year?

3) 250 calories x 365 days = 91,250 calories. Since there are about 3550 calories per pound of body fat, the person would gain 25.7 lbs. in the course of a year.

4) Now let’s suppose that we project the trend into the future. Suppose that the person continues to eat 250 too many calories per day for a decade. At the end of ten years, when the person is 30, he will have gained 257 lbs. and can be expected to weigh between 400 and 500 lbs.

Know very many 30-year old people who weigh between 400 and 500 lbs?

Didn’t think so.

Even people who give no attention at all to their caloric intake (such people being legion) do not usually gain 26 pounds a year or end up weighing between 400 and 500 pounds by the time they are thirty.

The only possible explanation for this is that the great majority of people–even overweight people–are not overeating more than 250 calories a day.

Now let’s flip the situation around:

5) Suppose that the same 20-year old person underate by 250 calories per day? How many pounds would he lose in a year? That’s right 25.7.

6) And what would happen in a decade? He’d be dead.

If he were magically able to continue losing weight evenly throughout the decade, he would have exhausted his entire body mass before the decade was up. In reality, though, unless you are The Incredible Shrinking Man, you can’t continue to lose body mass indefinitely. You’d probably die around the time you hit 70-90 lbs.

This means that people do not undereat by more than 250 calories per day, either.

Except for a the rare cases of a few individuals who starve themselves to death or who gain 250 pounds in a decade, most people consistently stay within an average of 250 calories of where the number they need to metabolize each day or within about 10% of the needed amount.

Further, even people who give no attention at all to their diet do this. The only conclusion is that there is a mechanism in the human body that pushes us to stay within that range of our needed caloric intake. (In actuality, the range is narrower than I have indicated, but I wanted to use simple obvious numbers to make the point.) Our bodies have a “weight regulator” fuction that works like a thermostat, keeping our caloric intake within a modest range of the number of calories we need per day.

From a phenomenological perspective, the tools the body uses to keep us in that range are feelings of hunger and satiety. When the body wants to jack up our calorie intake, it hits us with feelings of hunger. When it wants to tamp down our calorie intake, it hits us with feelings of satiety.

This means that the great majority of overweight people are not simply gluttonously sucking down food. If they were, their weight would quickly spiral out of control and keep going up until they died. Instead, they are simply eating when their body tells them to eat and not eating when it tells them to stop. In other words, they are responding to the biological imperative that is implanted in them.

Now, for obese people something has obviously gone wrong with the situation or they wouldn’t be overweight, but for most the problem is not the vice of gluttony. They are simply doing what their body is telling them to do.

I don’t have space in this blog entry to talk about what has gone wrong or how it can be fixed, but I’ll be happy to do so if folks want me to.

For now, we need to bear the above in mind when we are tempted to look down on people who are overweight–or who are more simply overweight than we are. Unless they’re experiencing rapid weight gain at the moment, they’re not eating beyond what their bodies are asking them to.