Junkfood Science: The question of the week: Diet or Exercise?

February 25, 2007

The question of the week: Diet or Exercise?

The news recently reported on a carefully-done study which debunked a number of widely-held beliefs about the best ways to lose weight. Not surprisingly, the media missed the full story.

Reuters Health reported:

No need to diet and exercise to lose weight

...Researchers report that dieting alone is just as effective as dieting plus exercise....Therefore, if the goal is purely shedding pounds, diet or exercise will work, according to this study....

The study also found that exercise did little to tone specific areas of the body. Fat was reduced consistently across the whole body and not more in any one trouble spot....This suggests that people are "genetically programmed for fat storage in a particular pattern and that this programming cannot be easily overcome by weight loss,” the authors note.

This and other news stories were taken from a press release describing a study by Leanne Redman, Ph.D. and colleagues at the Pennington Biomedical Research Center in Baton Rouge, LA:

The researchers conducted a randomized, controlled trial to examine the effects of diet alone or diet plus exercise in overweight but otherwise healthy study participants. The participants were divided into three groups. One group only reduced caloric intake. A second group reduced caloric intake by a smaller amount, but included exercise as part of their program, and a third set of participants served as a control group. They were all followed for a six-month period.

At the end of the study, the reduced caloric intake group and the group that combined a smaller amount of reduced calories with exercise had similar results. Members of both groups lost roughly 10 percent of their body weight, 24 percent of their fat mass and 27 percent of their abdominal visceral fat, which is fat buried deep in the abdomen and linked to heart disease risk....The researchers also discovered that fat distribution was not affected by either approach. The exercise group was not able to eliminate fat in certain parts of the body: so much for sit ups!

“We found that fat is reduced consistently across the whole body and not more in any one part,” says Redman. “We found some evidence in other studies that suggested the way in which we store fat is linked to our genetics and our study then would indicate that weight loss cannot override the way in which any individual stores fat. Perhaps an apple will always be an apple, and a pear, a pear!” ....

In other words, regardless of how each person increased their calorie deficit by 25% — through eating less alone or dieting and exercising more — they lost the same amount of weight and body fat at the end of 6 months. The 35 study participants were tightly monitored to ensure they followed the precise diets and exercise prescriptions. Their foods were prepared by the Center’s metabolic kitchen throughout most of this study and their compliance was monitored through food records and weight changes. Their 5 days a week exercise regimen consisted of 45-53 minutes of treadmill, stationary bike or stairmaster performed under supervision at least 3 times a week, during which their oxygen uptake was measured by indirect calorimetry and cardiovascular monitoring.

These researchers carefully measured the percentage of body fat at the beginning and end of the study using dual energy x-ray absorptiometry; and computed tomography (CT) was used for visceral fat distribution in the abdomen, liver and spleen. This study’s findings did not support popular claims that exercising — even aerobic exercise 5 days a week — during a diet can prevent the loss of lean body tissue and increase the loss of fat. Nor were efforts at spot reducing effective because our body shapes and where we store fat are primarily determined by our genes and not what we eat or our exercise.

Before we look at the effects of exercise, let’s look closely at the calorie reduction part of the trial because it actually debunks some of the most popularly-believed myths about obesity.


The participants in this study, besides being incredibly good sports about having every minutiae of their bodies and lifestyles examined and micromanaged for six months, were all healthy middle-aged Americans without a history of obesity, eating disorders, heart problems, diabetes or smoking. Their average body mass index (BMI) was about 27, which, until the definition for “overweight” was changed to a BMI >25 by the U.S. National Heart, Lung and Blood Institute in 1998, wouldn’t have even been considered overweight. Today it is, of course, as the new definition added more than 30 million average Americans to the rosters of “overweight.” The men in this study weighed an average of 195 pounds and the women 165 pounds, almost exactly what the U.S. CDC National Center for Health Statistics most recently reported is average for American adults. The study participants were also not obsessive exercisers because people who exercised more than twice a week were excluded. In other words, the calories they needed to maintain their weight were not unusual or extraordinary, but fairly typical for American adults.

The researchers then precisely calculated the baseline calories each person required to maintain their weight using 14-day doubly-labeled water assessments and 14-day in-house closely controlled feedings. They found that the study participants needed an average of 2,768 calories a day to maintain their weight.

Let’s stop right there for a moment. The U.S. CDC National Center for Health Statistics has monitored the daily calories consumed by American adults since 1971. Their latest National Health and Nutrition Examination Survey (NHANES) reported that the average American eats 2,240 calories a day (1,877 among women, 2,618 in men). [We’ll examine later the fallacies behind the claims of an increase over the decades.]

So, average American adults are eating less than calculated to maintain stable weights, not "overeating" as popularly believed.

Bottom line, the facts continually do not support the popular mythologies about fatness being just a matter of calories in and calories out, nor the beliefs that Americans are eating more calories than they “should,” never mind nutrition.

You’ll often see claims being made, typically by activists or those who believe we are not eating “right,” that Americans now eat an average of 2,700 calories a day or the even more ridiculous claim that our average calorie intake has skyrocketed to 3,817 calories a day!

The source of these erroneous beliefs is U.S. Department of Agriculture Economic Research Service data. This is economic information on the supply of food produced in this country, which currently equates to 3,900 calories per person. The term “food consumption” used in these economic reports is a calculation made by dividing food disappearance figures by the population. But extrapolating dietary intakes from food supply data has been repeatedly shown to be faulty and to wildly exaggerate actual consumptions.

Economists at Harvard Institute for Economic Research noted that only in recent years has wastage been accounted for — which they’ve found done imprecisely at best. More significantly, it doesn’t consider industrial and other uses for foods, which are extensive. As David Klurfeld, Ph.D., professor and chairman of the Department of Nutrition and Food Science at Wayne State University, editor-in-chief of the Journal of the American College of Nutrition and Nutrition New Focus wrote about the “absurdity” of using this data to estimate what Americans actually eat: “...soybean oil is used to make ink, lubricants, diesel fuel, plastics and many other useful products....and the U.S. feeds millions more people outside the country and we don't have to eat six meals a day to get rid of surplus crops.” Even school kids know George Washington Carver developed more than 300 uses just for peanuts — from paint, explosives to kitty litter! And Midwest-grown corn is becoming ethanol to fuel our automobiles and farm equipment. Perhaps kids have more common sense than most of us.

In this study, after 6 months of reducing their calories by 25%, the women had lost about 17 pounds and the men about 20 pounds — about 3/4 pound a week. But this study merely showed short term results, not lasting changes. As researchers have repeatedly shown, regardless if weight loss is achieved by diet or exercise, over the long term any meaningful initial weight loss is regained within the first year and virtually all of it by 5 years.

Weight loss the wrong focus

Interestingly, the press release gives the impression that weight loss is important for health benefits. This idea is certainly important to the center where this research was conducted. The 403,000 square-foot Pennington Center, which opened in 1988, is led by Claude Bouchard, Ph.D., outgoing president of the International Association for the Study of Obesity and the world’s largest organization of groups working on the “obesity crisis.” As the Social Issues Research Centre reported, IASO and related special interests are funded largely by major pharmaceutical companies. Pennington’s website notes that in 2002 it received the largest grant in its history from the National Institutes of Health which awarded it $12.4 million over seven years to investigate the benefits of calorie restriction.

Other Pennington researchers, however, have published studies examining the risks and benefits of weight loss and not found good support for this popular view. As Donna Ryan, M.D., at Pennington and a consultant for Abbott Pharmaceutical Company noted in a recent European Heart Journal article, a number of epidemiological studies have associated weight loss with increased mortality:

The Framingham study is one of many studies which have shown a negative relationship between weight loss and mortality. Over an observation period of 20 years, and omitting deaths in the first 4 years, deaths were highest among those who lost weight, even when the data were adjusted for age, BMI, smoking, and other risk factors: compared with subjects whose weight did not change, there was a 44% increase in total mortality rate in men who lost weight and a 38% increase in women who lost weight. Many other studies have shown the same relationship. In addition, some of the studies have demonstrated that this relationship exists whether the individual is overweight, normal weight, or underweight.

In view of the observations from these large epidemiological studies, it is valid to question the health benefits of weight loss.... It has also been demonstrated in numerous studies that weight loss in patients with chronic heart failure is associated with impaired survival.

Dr. Ryan noted numerous studies demonstrating a wide range of harmful effects of dieting and weight loss. She also pointed out that only intermediary factors associated with obesity (not actual clinical outcomes) have been shown to be affected by intentional weight loss measures but that “data from randomized controlled trials will be needed to convince epidemiologists that weight loss is beneficial to health.” The Look AHEAD (Action for Health in Diabetes) trial to examine the effects of weight loss on fat people with type 2 diabetes is underway, she said, and results are expected in 2012. But to date, there is no clinical evidence among people to demonstrate any actual benefits to lifespan from dieting and weight loss.

In contrast, she failed to note the countless studies demonstrating that fatness itself has nothing to do with health and longevity. One of the largest and most famous is the Aerobics Center Longitudinal Study of 25,389 men examined at the Cooper Clinic in Dallas, Texas, from 1970 and followed to their death or until December 31, 1989. Research at the Cooper Institute of Aerobics Research also examined more than 113,000 women. The Cooper Institute is where much of the country’s landmark research on fitness and preventive health has been conducted. Research there has consistently found that being fat does not determine increased mortality risk and that physical activity and fitness — not body weight or waist measurements — are what matter in lowering risk. And despite the stereotypes of what “fit” looks like, they found that about half of “obese” adults are highly fit on maximal exercise testing, not much different from the slender people.

Dr. Timothy S. Church, M.D., M.P.H., Ph.D., now at Pennington Biomedical Research Center, discussed the many controlled randomized trials examining risks and cardiovascular and lifespan benefits of exercise in a December 2006 Medscape examination of exercise in evidence-based medicine. Also participating was renowned aerobics researcher, Steven Blair, PED, currently a professor in the Arnold School of Public Health at the University of South Carolina. Health and longevity are not determined by body mass index or weight, but are influenced by physical activity and fitness, they said. Being active cuts overall mortality in half for both men and women. As has been shown by the research Church and Blair conducted while at the Cooper Institute, exercise not only helps people live longer, it lowers heart disease, stroke, type 2 diabetes and cancers, strengthens bones, reduces stress and improves immune system function. “Fitness is a more powerful predictor of mortality than BMI,” said Blair.

But instead of the word “exercise,” said Dr. Church, we should be saying “physical activity” because formal exercise isn’t required to see health benefits. And it doesn’t take much to see benefits while simultaneously eliminating the risks associated with “exercise:”

When you tell them what it takes, they're surprised by how little it takes. And the basic recommendation still stands of 150 minutes a week, which breaks down into 30 minutes a day 5 days a week of moderate-intensity physical activity....Walking. It's just walking....It's little things that add up through the day. And it just doesn't take that much.

Walking, gardening, housework, bicycling, swimming, dancing, golfing, woodworking or other hobbies and activities enjoyed in our daily lives all count as “activity.”

If all of this is really about health and well-being, then…

Leotards, gyms, team sports and athletic gear are not required. :))

Dieting and achieving bodies that look “fit” are not required. :))

The headline for that Reuter’s news story was actually more accurate than it realized.

© 2007 Sandy Szwarc

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