Study highlights the role of exercise in weight control

A surprising study and little bemusing blog toured Stanford last week after suggesting that weight gain U.S. during the last 30 years is bound to more than the number of calories apply to people.

The results contradict the way health experts have found, and the obesity rate in the country, which grew strongly explained in the same three decades. For several years, most of the blame fell on the consumption of calories rather than fitness.

Many experts questions based on the weight - even the authors of the study from Stanford - were quick to challenge the final results, or at least how they are interpreted. However, the results are at least amplify a fact that requires a lot of time in the field of obesity research: It's complicated.

"I'm not sure if we ever to have accurate numbers and explanations - and I'm not sure that it's necessary," said Dr. Uri Ladabaum, a gastroenterologist at Stanford University and author of the new study director.

"The messages can be confusing when a study came saying something and meaning another," he said. "But if we look at the big picture and common sense, we can see that two things are important."

Growing Problem

More than two-thirds of Americans are overweight or obese, such as body mass index, defined a measure of the size and weight. The negative health effects of obesity are controversial, but not for obesity, which the people in risk for diabetes and other metabolic diseases, and can cause premature death.

Despite decades of study, the health authorities can not say for sure what to massive weight gain of Americans, but it is more likely that a combination of factors - the cultural and behavioral changes, the quantity and quality of calories consumed, and an obligation to accept physical activity.

"There's really no reason to play physical activity from power, since both absolutely crucial - both for good health and the prevention of obesity," said Dr. Kirsten Bibbins Domingo, co-director of the UCSF Center for Vulnerable Populations at San Francisco General Hospital. "This study is very complex, so for me to simplify the message."

Undoubtedly, the benefits of exercise. Regular physical activity has been shown to lower blood pressure, reduce stress, help diabetes and people to sleep. Exercise can protect and improve bone density and joint health with age the disease from heart disease and Alzheimer's.

It also helps people to lose weight and keep, but its role is controversial. In recent years, in particular, the experts in weight loss, pointed to food and caloric restriction particularly by far the most important factor for losing pounds.

There is even a popular saying in the circles weight loss: one can not escape a bad diet.

"You can eat a Big Mac in 15 minutes, and takes about an hour to get the bike fit," said Patricia Crawford, co-director of UC Berkeley for weight and health. "There is no comparison - there is no way we can carry out a diet days are not long enough.".

But it is a mistake to minimize the importance of exercise when it comes to weight loss, Crawford said. He was a member of the Committee of 16 members that share the Institute of Medicine report in 2012 about obesity in America. One of the focal points of the report: The Americans need to increase physical activity.

The Stanford study says that up.

The study, published in the August issue of the American Journal of Medicine, analyzed weight data and the results of the survey of more than 20,000 people in the United States between 1988 and 2010.

The analysis revealed that self-reported consumption of calories does not change during the long period, but the percentage of people who had no exercise, said increased dramatically. Meanwhile, the body mass index and waist circumference increased slowly but steadily over the years.

It is important to note that the study has limitations. Calorie intake and activity on surveys of participants who have not accurately reported their data can based.

The results of the calories differ from the results of similar studies, including the report of the Institute of Medicine, obesity, noting that Americans consume about 150 to 300 calories per day more than it is now two or three decades.

Measures of physical activity in the Stanford study were particularly problematic because the way the participants were asked changed over time, so it's not really fair to compare the latest reactions to the results of previous years.

But if it's an important lesson, which is, in spite of the limitations is that the practice questions - lots of Ladabaum said.

"The key is to pay attention to two things - diet and exercise," said: "If there is something good that can come out of this supply in our study, is the focus of the two factors.".

Not all who exercise in

According to the Stanford study, the data from the National Survey of Health and Nutrition Examination analyzed, 43 percent of men reported no physical activity at all in 2010, and a surprising 52 percent of women said the same.

The data are similar studies that show Americans are not nearly enough exercise and are widely supported by the fulfillment of the national guidelines that require moderate activity 150 minutes per week.

However, many people reported a complete lack of movement is a surprising result, also used for public health experts to complain against poor exercise habits of Americans.

"What is worrying is the number of people who are completely sedentary -., The they are not physical at all" activity, Bibbins-Domingo, "said is very important that people do, whatever their goals, more physically fit although weight loss not come immediately. "

The importance of this part varies the role of exercise in weight control something like the people to lose weight or trying to maintain.

Doctors have shown in several studies that regular exercise is important, especially after someone lost weight maintenance, a lot of weight. The idea is that people who have lost 30 pounds or more have significantly reduced the number of calories you need to eat to maintain your weight - 150 pounds a woman who lost 50 pounds, about 300 calories less per day would be required to keep their weight back.

In the process of weight loss, which means that few women consume less calories a progressive loss. But in the end, he retired to his 300 calorie daily diet. When she focuses on weight loss, it may be convenient to limit food intake, but may be less tolerant calorie restriction when dealing with a stable outlook.

This exercise can be critical. Someone who works hard every day or almost every day of the week, you can easily burn 300 calories and compensate.

But the amount of exercise helps you lose weight - or lack of exercise leads to weight gain - it is not so clear.

Some reports have suggested that the more people exercise, the more you will be able to control your appetite and of course they have the right amount of calories, the Co-Director of the Program Management Medical Weight Dr. Wayne Smith consume, said Kaiser Permanente in San Jose.

Physical activity can also be a shot in the arm that help people be to maintain a weight loss plan, Smith said. And even if someone burn 100-200 calories in a daily walk, it may be sufficient to create a calorie deficit and increase weight loss, albeit very slowly.

Common Mistakes

The errors that can make people to accept that physical activity alone is enough to lose weight, or activity gives them the freedom to derail a diet. Isabella Pazmino, owner of a Curves gym in San Francisco, said that despite the realization that energy can prevail over the year.

"People are encouraged to" run, run, just get out and go, "so many people, I think that's enough. And no," said Pazmino. "For someone who is extremely overweight and lack of exercise, walking is a good start, and it's better than doing nothing. But that's not enough."

However, he said, is that people exercise to lose weight or health, or just for fun, there is one thing that is not in dispute.

"Exercise is not an option - not a luxury," Pazmino said: "It is a necessity.".

Erin Allday is a writer for the San Francisco Chronicle. E-mail: eallday@sfchronicle.com