Food or Exercise?


I spend a lot of time thinking about which is more important for weight loss and health—food or exercise. I have always believed that exercise is more important, that one really can outrun a bad diet, perhaps because I don’t ever want to give up chocolate or sugar cereals. Admittedly, I’m biased. But not in the way most people think. I’m not biased because I’m a lifelong daily runner who eats sugar cereals and still weighs the same as he did in high school 27 years ago. I’m biased because of my education. I don’t believe one can go through so many years of school and read and be involved with so much research and come away with any conclusion other than that exercise is more important than diet. While many (most) people will disagree with me, science doesn’t.

The scientific research on weight loss shows a number of things, including:

1. Diet plus exercise provides greater weight loss than diet alone.

2. The amount of aerobic exercise is closely linked to body weight. More exercise equals lower body mass index and body circumferences.

3. Starting vigorous exercise and stopping it decrease and increase, respectively, body weight and intra-abdominal fat, with the changes proportional to the change in amount of exercise.

4. Exercising more than 250 minutes per week is needed for significant weight loss and for weight maintenance.

5. Weight regain is related to decreases in physical activity during weight loss.

6. The exact macronutrient composition of a person’s diet doesn’t matter as much as the total number of calories consumed.

7. To lose weight, diet (cutting calories) is more important than exercise; to keep weight off, exercise is more important than diet. 

I came across an article that was posted online last week, in which one of my colleagues at the University of Colorado-Boulder also says that carbs are not the enemy and exercise is more important than food. You can read the article here. I shared this article on social media and, of course, many people chimed in, because when it comes to weight loss and diet, many people have strong opinions, most of which are based on their experiences.   

The reason why exercise is more important than food is because of what exercise can do for our bodies that food alone cannot do: provide a strong stimulus to which our muscles and metabolism adapt. No one will argue that food isn’t important, because of course it is, but food doesn’t make us fitter. Only exercise can cause muscles to change their metabolic profile by affecting mitochondria to become better fat burners. 

If we take two people, and one eats perfectly clean with a nutrient-dense diet and no processed foods but doesn’t exercise much, and the other runs a lot and does resistance training but has a mediocre diet with the occasional Twinkie or chocolate chip cookie, who is going to look better and be fitter? The latter. 

I’m pretty sure I didn’t get my sculpted legs and ass from eating kale salads; I got them from running six days per week for 33 years. And so it is for other people who exercise.

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