What’s Driving America’s Obesity Problem?

Currently, nearly two-thirds of Americans are overweight. By 2030 it is estimated more than half our population may be clinically obese. Childhood obesity has tripled, and most children will grow up to be overweight as well. The United States may be in the midst of raising the first generation, since our nation’s founding, that will have a shorter predicted life span than that of the previous generation.

The food industry blames inactivity. We just need to move more, they say. But what is the role of exercise in the treatment of obesity?

“There is considerable debate in the medical literature today about whether physical activity has any role whatsoever in the epidemic of obesity that has swept the globe since the 1980s.” The increase in calories per person is more than sufficient to explain the U.S. epidemic of obesity. In fact, if anything, the level of physical activity over the last few decades has actually gone up in both Europe and North America.

This has important policy implications. We still need to exercise more, but the priorities for reversing the obesity epidemic should focus on the overconsumption of calories. American children are currently eating about an extra 350 calories (equal to about a can of soda and small fries), and adults are eating about an extra 500 calories (equal to about one Big Mac).  We’d have to walk two hours a day, seven days a week to burn off those calories. So exercise can prevent weight gain, but the amount required to prevent weight gain may be closer to twice the current recommendations. It’s more effective to stick to foods rich in nutrients but poor in calories: see my video Calculate Your Healthy Eating Score. It’s cheaper too, see Best Nutrition Bang For Your Buck.

Public health advocates have been experimenting with including this kind of information. One study found that fast food menus labeled with calories and the number of miles to walk to burn those calories appeared the most effective in influencing the selection of lower calorie meals.

Exercise alone may have a small effect, and that small effect can make a big difference on a population scale. A 1% decrease in BMI nationwide might prevent millions of cases of diabetes and heart disease and thousands of cases of cancer. But why don’t we lose more weight from exercise? It may be because we’re just not doing it enough. “The small magnitude of weight loss observed from the majority of exercise interventions may be primarily due to low doses of prescribed exercise.”

People tend to overestimate how many calories are burned by physical activity. For example, there’s this myth that a bout of sexual activity burns a few hundred calories. So may think, “Hey, I could get a side of fries with that.” But if we actually hook people up and measure energy expenditure during the act (and the study subjects don’t get too tangled up with all the wires and hoses) it may be only close to the metabolic equivalent of calisthenics. Given that the average bout of sexual activity only lasts about six minutes, a young man might expend approximately 21 calories during sexual intercourse. Due to baseline metabolic needs, he would have spent roughly one third of that just lying around watching TV, so the incremental benefit is plausibly on the order of 14 calories. So maybe he could have one fry with that.

But don’t get me wrong—exercise is wonderful! Check out, for example: What Women Should Eat to Live Longer and Halving Heart Attack Risk.

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live year-in-review presentations Uprooting the Leading Causes of Death, More Than an Apple a Day, and From Table to Able.

Nutrient-Dense Approach to Weight Management
Eating Better to Look Better
Increasing Muscle Strength with Fenugreek


Elaine W.
Elaine Wabout a year ago

Good facts to know. Thanks.

aj E.
aj Eabout a year ago


Jeanne Rogers
Jeanne Rabout a year ago

Thank you for sharing.

Tanya W.
Tanya Wabout a year ago

Noted 🏄

Tanya W.
Tanya Wabout a year ago

Thank you

Fi T.
Past Member about a year ago

We are not born to sit

Sybil G.
Sybil G3 years ago

Inactivity, my butt!

Try sugar, sugar, sugar, sugar, sugar, sugar, sugar and more sugar... Sugar in cereal, cookies, bread, crackers, ketchup, tomato sauce, sodas, dressings, coconut water, energy drinks and bars, soups, chocolate, candies, ice creams... Everywhere, that goddamn sugar!

Recipe: 1-1/2 tightly packed cup of sugar in a cake 2 cups of icing sugar for the frosting...

Fake sugar, high fructose corn syrup, honey, glucose, inverted rice syrup, molasses... Are you kidding me?!
When you cut the unjustly vilified saturated fats from everything, what do you replace them with? Well, hello sugar... Taste good, huh? Too bad it's making you fat.
Oh, by the way, I don't care what anyone else say: fat is not beautiful.

Magdalena J.
Past Member 3 years ago

Thank you!

Jane Davidson
Jane Davidson3 years ago

Genetically engineered wheat, which is the only wheat available and our diet staple, is a major culprit.

Mary Deforest
Mary Deforest3 years ago

The food pyramid with a strong overwhelming base of carbohydrates that the body thinks is sugar. Thank you FDA for setting this off. People grew up on this and continue this. Then add the normal junk food, single working parents and working parents that are struggling time wise to get food on the table before the kids eat the furniture. That a child can't even safely play in the yard, walk next door, etc, or a lunatic will kidnap them, a drunk will drive over them, a sexual predator will snatch them, or a dog will eat them alive.
This week, we just had a father walking his 3 year old son and dog, when a lunatic came up and tried to snatch his son. She then jumped in her car and ran over the father's legs--sadly and fortunately-he had prosthetic legs-so he wasn't injured. Fortunately people were in their front yards and other people were walking. Someone grabbed the child from the lunatic and ran like ***###, while she was trying to get the kid in the car, and the dog was biting the lunatic. Everyone called 911, and threw rocks at the lunatic's car. A police car just happened to be coming down that road, and caught the lunatic.
She still says the boy is her son. I'm not making this up. She was charged yesterday for attempted kidnapping, child abuse, animal abuse (the poor dog), using a vehicle with the intent of causing bodily harm, assault with a dangerous weapon, interfering with parental custody. I told my son they should add distracted driving-that might keep her in cu