Physical activity may not be key to obesity epidemic

January 6, 2009

A recent international study fails to support the common belief that the number of calories burned in physical activity is a key factor in rising rates of obesity.

Researchers from Loyola University Health System and other centers compared African American women in metropolitan Chicago with women in rural Nigeria. On average, the Chicago women weighed 184 pounds and the Nigerian women weighed 127 pounds.

Researchers had expected to find that the slimmer Nigerian women would be more physically active. To their surprise, they found no significant difference between the two groups in the amount of calories burned during physical activity.

"Decreased physical activity may not be the primary driver of the obesity epidemic," said Loyola nutritionist Amy Luke, Ph.D., corresponding author of the study in the September 2008 issue of the journal Obesity. Luke is an associate professor in the Department of Preventive Medicine and Epidemiology at Loyola University Chicago Stritch School of Medicine.

Physical activity is defined as anything that gets your body moving. U.S. government guidelines say that each week, adults need at least 2 ½ hours of moderate aerobic activity (such as brisk walking) or 75 minutes of vigorous activity (such as jogging). Adults also should do muscle-strengthening activities, such as weight-lifting or sit-ups, at least twice a week.

Physical activity has many proven benefits. It strengthens bones and muscles, improves mental health and mood, lowers blood pressure, improves cholesterol levels and reduces the risk of cardiovascular disease, diabetes, breast cancer and colon cancer.

But Loyola research suggests that weight control might not be among the main benefits. People burn more calories when they exercise. But they compensate by eating more, said Richard Cooper, Ph.D., co-author of the study and chairman of the Department of Preventive Medicine and Epidemiology.

"We would love to say that physical activity has a positive effect on weight control, but that does not appear to be the case," Cooper said.

The recent study included 149 women from two rural Nigerian villages and 172 African American women from the west side of Chicago and suburban Maywood.

Adjusted for body size, the Chicago women burned an average of 760 calories per day in physical activity, while the Nigerian women burned 800 calories. This difference was not statistically significant.

Diet is a more likely explanation than physical activity expenditure for why Chicago women weigh more than Nigerian women, Luke said. She noted the Nigerian diet is high in fiber and carbohydrates and low in fat and animal protein. By contrast, the Chicago diet is 40 percent to 45 percent fat and high in processed foods.

Results of the new study are similar to those of a 2007 study of men and women in Jamaica. Researchers from Loyola and other centers found there was no association between weight gain and calories burned during physical activity.

"Evidence is beginning to accumulate that dietary intake may be more important than energy expenditure level," Luke said. "Weight loss is not likely to happen without dietary restraint."

Source: Loyola University

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not rated yet Jan 06, 2009
Yes, it IS diet. The diet your body evolved to eat. Indigenous people become very unhealthy after changing diets from traditional to modern. The Pima Indians are one example. From eating native plants to frybread is not healthy.
I recommend The Metabolic Typing Diet for more information.
5 / 5 (3) Jan 06, 2009
Hilarity. Is there anything surprising about this article, really?

Just look at their hilarious numbers: Chicago women burn 760 calories, Nigerian women: 800 calories a day.

Do you think Nigerian women go and eat several Big Macs every day? A single Big Mac has 590 calories and over half of your daily value of saturated fat in it:

Eat 3 of them, plus several servings of potatoes fried in fat (fries), plus several cups of sugar water (coke), and it's no wonder there's an obesity "epidemic".

You eat >2000 calories (and bad ones too, that can't be processed easily and stick around), and burn 760 of them... uh, what do you think would happen? Your body can only poop so much of it out, it's not gonna magically disappear, the laws of physics won't allow it! :-p
5 / 5 (1) Jan 06, 2009
* I should add to my comment above, both of the calorie figures above (760 and 800), are only the calories burned from physical activity, they are *not* the total number of calories these women burned each day.

You burn calories just sitting, so the actual figure is higher, but it's a shame that the article didn't mention what that was, as that's the most important figure: how many calories did these women use up total per day, and how much did they take in.
not rated yet Jan 06, 2009
It is NOT the fat. It is the quality of fat that matters.
What your ancestors adapted to eat 50,000 years ago is the diet you should eat for optimum health.
5 / 5 (2) Jan 06, 2009
Its Diet exercise. My son is case in point, he was a bit chubby... then started to due intense physical exercise and he slimmed down a lot. My wife eats the same diet I do, but yet I'm slim, and she is not active.... ;)

So eat healthy (fruit, Veggies, etc.. etc..)and exercise.

BTW the occasional Big Mac and fries won't kill you, and if you like them, will make life more enjoyable. If I eat junk, then I exercise more.
not rated yet Jan 06, 2009
These researchers have a typical American conclusion. Reducing your excessive amount of calories intake and the lack of physical activities won't help you combat obesity (those "things" in starvation in Africa, refugee camps, the dredges of life doing hard labor..etc, were other species entirely, they do not confirm to the physical laws of energy intake-energy expenditure, you know). Perhaps they are trying to say let natural forces to eliminate the obeses from their excesses, while taxpayers will continue be footing the health care system bills while the obeses are dying (slowly, and keep them gainfully, meaningfully employed to do more such illuminating researches.
3.7 / 5 (3) Jan 06, 2009
lol, headline should read "American women fatter than Nigerian women, scientists baffled"
1 / 5 (1) Jan 06, 2009
Yes it certainly is the diet, namely the highly processed foods sold by food industry.

It's simple, from the market perspective the best food products are those which not only taste best but also induce people to eat as much of them as possible. The food products today on the market evolved towards that goal so they
1. Contain plenty of easily accessible energy to make them tasty
2. Might have altered nutrient compositions to avoid inducing the feeling of satiety after eating

Now 1 is obvious and it certainly plays a part in the problem but 2 is more complex. I don't know to what extent such tricks are successful and I don't know if there are companies doing it on purpose, but it certainly is a possibility so it should be further investigated in the face of the obesity epidemic.

How tricking satiety could be done, for example let's consider sugars but it is just an example and the same principle can be employed with aminoacids and fats also.
Foods contain various sugars but the two most common are glucose and fructose, lets say that both make food equally sweet but fructose is only 20% as effective at inducing the feeling of satiety. Now lets say natural foods have roughly equal amounts of the two, but thanks to modern processing capabilities we can produce foods with artificially raised fructose content and lowered glucose content. Such foods will be just as sweet and tasty as natural ones but they will be much worse at inducing satiety making you eat much more of them.
Foods altered that way will be more successful from business POV and might even displace their natural versions from the market.
Now THIS IS ONLY A HYPOTHETICAL EXAMPLE, I don't know how fructose compares with glucose in reality or if it's being used that way.

One thing to note is that if such tricks do work the food products will evolve to take advantage of them even if they are not consciously designed to do it, market forces will do the trick either way.

All this means American women who want to be as slim as Nigerian women need to cook their own food from raw products.
1 / 5 (1) Jan 06, 2009
"People burn more calories when they exercise. But they compensate by eating more." That's BS, if you exercise you release certain hormones that essentially tell your brain you're not hungry. Maybe if the exercise is exceedingly minimal it could work as described, but real exercise or hard work reduces your appetite, I know it did for me (hard work as opposed to exercise)
not rated yet Jan 06, 2009
Great idea: open a fast food restaurant in Chicago, call it "Nigeria Express", and serve the rural Nigerian diet. If Chicago women eat there and still get fat, we can conclude that it is just the city of Chicago, and not the actual food, that makes people fat.
5 / 5 (1) Jan 07, 2009
It is hindsight bias to assume that these results are "common sense". If the results came out that exercise is related to obesity levels, then people would be saying "duh" as well.

I would like to see studies conducted on the quality of foods people eat, especially since this is what this research's conclusion alludes to.

And to the commenter who basically said that it is unfair to compare women in North American women to African women because conditions are so much more harsh in Africa, I will say that your belief is very skewed. Africa is a huge continent and living conditions vary. Nigeria is hardly the hot bed of stressful living conditions. Maybe if this study compared Congolese or Sudanese women to those in Chicago then I would agree.

I'm reminded of a comment a very Western friend of the family made years ago after her rather plump daughter returned from living in Africa looking akin to a stick figure - "If you want to lose weight, go to Africa!" Or at least take up their dietary habits according to this study.
not rated yet Jan 07, 2009
It would make more sense to evaluate indigenous people who change their diets from traditional to 'modern'.
I understand a study like that exists in Australia. It would also be interesting to compare genetic ancestry to diet.
not rated yet Jan 11, 2009
184lbs for an African American woman in Chicago? Are you kidding me? That's an AVERAGE weight? Are they interbreeding with Samoans? I mean, I suspected a problem was brewing but .......184lbs?
That's my weight goal but I'm a 6'3" male.
not rated yet Jan 11, 2009
Nice article, and, I think, an important paper. I would like to know the caloric intake differences between urban Chicago and Nigeria. OTOH, a daily difference of 40 calories, over a year is 4 pounds, a decade is 40 pounds. I was dismayed recently by some nephrology literature showing the toxic effects of a high fructose diet (to mice) causing obesity, hypertension, hyperuricemia, and renal insufficiency, which frankly scares me about our national agenda to promote high fructose corn syrup as a food staple.
not rated yet Feb 06, 2009
Gary Taubes, in "Good Calories, Bad Calories" covers in detail the science of the last hundred years. Our fat is controlled by insulin. If we eat so that the insulin spikes by eating refined carbohydrates, the excess insulin exactly encourages the fat cells to grow fatter. Thus Dr. Atkins was right. Regardless whether you eat a high fat diet, if you eat a low carb diet, you will lose fat. While he thought there must be a fat mobilizing hormone, it turns out that that function is performed by low levels of insulin. The reason calorie restricted diets don't work, long term is that the stomach, noticing "starvation" emits ghrelin which elevates the appetite, suppresses your entire metabolism, and makes your fat cells greedy. Yo-yo dieting anyone? Exercise is good for your health, but carbs via insulin control your fatness. Further, exercise raises your appetite, just like your grandmother knew.

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