Файл: Medical_Myths_Lies_and_Half-Truths_guidebook.pdf

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Eades, 

The Doctor’s Complete Guide to Vitamins and Minerals

. 

Shils et al., 

Modern Nutrition in Health and Disease

.

1. 

Should everyone be taking vitamin supplements?

2. 

What is the best way to achieve healthful nutrition?

    Questions to Consider

    Suggested Reading

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Lecture 4: Dieting—Separating Myths from Facts 

Dieting—Separating Myths from Facts 

Lecture 4

You don’t want to get involved in some kind of elaborate scheme that 
you’re not going to be able to really maintain long term, like counting 
every single calorie. It’s better to use something that is simple and easy, 
that you can do every day for the rest of your life, and that will help you 
estimate and keep general track of how many calories you’re eating. 
This includes just writing down what you eat. If you do that—just 
record what you eat—that helps people lose an additional 10% or 20% 
of weight.

D

o you want to know the secret to weight loss? There are quite a 
number of self-help books, videos, and other products all trying to 
sell you that secret. How many times have you heard the claim “lose 

weight without diet and exercise?” This lecture examines diet—what we eat, 
what we should eat, what we perhaps shouldn’t eat, and how much we eat. 

How many calories does an average person need on an average day? That 
depends on a number of variables, speci

¿

 cally height, weight, age, and level 

of activity. An average man needs to eat about 2500 calories per day in order 
to balance his energy expenditures; an average woman, around 2000 calories. 
Of course, somebody with a very high degree of activity or someone above 
average in size may need to eat as many as 3000 calories in an average day.

Basal metabolic rate measures how many calories we burn going about our 
business. This is calculated based on our height, weight, and age. The basal 
metabolic rate increases with increasing height and weight and decreases 
with age. You also have to adjust the basal metabolic rate for activity 
level. Somebody who is sedentary isn’t going to burn as many calories as 
somebody who is highly active. Putting all those factors together can allow 
you to roughly calculate how many calories you burn each day.

Weight management simply comes down to calories consumed versus 
calories expended. Overeating by as few as 50 calories per day can result 
in as much as 5 pounds gained per year. That’s a lot of weight gain for a 

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very tiny difference in our eating habits. So what if you want to lose some 
excess weight? A conservative approach to weight loss is underconsuming—
consuming fewer calories than you burn by about 500 per day. If you 
underconsume by 500 calories 
per day, that’s 3500 calories, or 1 
pound, per week. One pound per 
week is a good, healthy rate of 
weight loss. 

At the more aggressive end 
of the spectrum would be 
underconsuming by about 1000 
calories per day. Most people 
cannot sustain that signi

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 cant  a 

decrease in their daily food intake 
for any period of time. Even still, 
underconsuming by 1000 calories 
per day only results in a weight 
loss of about 2 pounds per week. 
What this also means is that, if 
someone is claiming you can lose 
5, 10, 15, or 20 pounds in 1 or 2 
weeks, they’re being less than 
honest. You can only burn about 1 to 2 pounds per week of fat, which is what 
you want to lose when you’re trying to lose weight. Any weight loss above 
and beyond that is water weight or other things. 

Lots of people claim to have tricks and tips for losing weight. Unfortunately, 
none of them are terribly helpful. One you may hear about is fasting, jump-
starting a diet by fasting for a day or longer. There’s really no evidence for 
any long-term or signi

¿

 cant bene

¿

 t from fasting, and it shouldn’t be part of 

a weight control or weight management program. In fact, fasting may cause 
your body to try to conserve calories and lower its metabolic rate. 

What about late-night eating? A lot of people give the advice that you 
shouldn’t eat late at night if you’re trying to lose weight because those 
calories turn directly into fat. This has been studied multiple ways in both 

Sensible eating and regular exercise 
are the best ways to maintain a 
healthy weight.

© BananaStock/Thinkstock.

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Lecture 4: Dieting—Separating Myths from Facts 

animals and humans. It turns out that it really doesn’t matter when you 
consume your calories; the net calories will still be stored if you have excess 
calories. It still comes down to calories in versus calories out. 

What about restrictive diets? A lot of fad diets or weight loss diets are 
premised on the notion that if you eliminate certain things from your diet, the 
weight will magically melt away. This is not a helpful strategy or a helpful 
approach to weight loss. In the 

¿

 nal analysis, it doesn’t really matter what 

kinds of calories you’re eating; 
the overwhelmingly important 
factor is how many calories you’re 
eating. Also, by restricting the 
variety of food that you eat, you 
can compromise good nutrition. 

In the last 20 years or so, there has 

been a huge fad of diets focused on either low fat or low carbs. The notion 
here is that if you adjust the proportion of macronutrients—fats, proteins, and 
carbohydrates—in your diet, you will get to some magical zone or magical 
balance in which you’ll shift into a different kind of metabolism that will 
help you burn calories. After a lot of research, it turns out that there just isn’t 
evidence to support these claims. It all still comes down to caloric intake. 

I’ve spoken a lot about food and how much we eat. What about exercise? 
Isn’t exercise important for weight loss? It turns out the answer is yes and 
no. Exercising de

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 nitely burns calories, but not as many as you may think. A 

reasonable exercise program is to do 30 minutes of cardiovascular exercise 
3 days a week. That would burn about 450 calories. If you’re trying to 
underconsume by 3500 calories per week in order to lose 1 pound per week, 
then burning off an extra 450 calories doesn’t get you very far toward that 
goal. The bottom line is that you can’t lose weight solely by exercising. You 
would have to exercise 90 minutes a day, 7 days a week, in order to burn off 
1 pound per week. Thus you have to combine exercise with calorie control.

What about diet pills—is there any medicine or pill that will help in a 
weight loss program? There’s no theoretical reason why there can’t be a 
pharmaceutical, for example, that shifts us into more of a weight loss balance. 

Exercising de

¿

 nitely burns 

calories, but not as many as 
you may think.

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But nothing has been proven to be both safe and effective. That doesn’t stop 
there from being many “weight loss pills” on the market that claim to melt 
away the fat without diet and exercise. I certainly wouldn’t believe any of 
those claims.

The way I interpret that breadth of research is simple. Dieting doesn’t work. 
Perhaps that’s the biggest myth of all—that you can positively impact your 
weight maintenance by going on a diet. Rather, the focus should be on long-
term, healthful strategies that you can maintain for the rest of your life. 

Ŷ

Novella, “The Skeptic’s Diet.”

Rippe, 

Weight Watchers Weight Loss That Lasts.

1. 

Is there any way to achieve and maintain a healthy weight without diet 
and exercise?

2. 

What does the scienti

¿

 c evidence have to say about popular weight 

loss diets?

    Suggested Reading

    Questions to Consider