To Evolution

Exercise can help you lose weight. Provided you do enough

    Abdulaziz Sobh
    By Abdulaziz Sobh

    Categories: Beauty & Fitness, Health


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    Can you help us lose pounds after all?

    A new and provocative study involving overweight men and women suggests that you probably can, underestimating the widespread notion that exercise, by itself, is not worth losing weight.

    But the findings also indicate that to benefit, we may have to exercise a little.

    In theory, exercise should contribute substantially to weight loss. Burn calories If we do not replace them, our bodies must achieve a negative energy balance, use stored fat as fuel and shed pounds.

    But life and our metabolisms are not predictable or fair, as shown by the multiple studies of exercise involving people and animals. In these experiments, participants lose less weight than would be expected, given the energy they expend during exercise.

    Studies have generally concluded that athletes had compensated for the energy they had expended during exercise, either by eating more or by moving less throughout the day. These compensations were often involuntary but effective.

    However, some researchers began to wonder if the amount of exercise could be important. Many of the past human experiments involved approximately 30 minutes a day of moderate exercise, which is the amount generally recommended by current guidelines to improve health.

    But what would happen if people exercised more? Some researchers asked. Would they still compensate for all the calories they burned?

    To find out, scientists at the University of North Dakota and other institutions decided to invite 31 overweight sedentary men and women to a laboratory to measure their resting metabolic rate and body composition.

    The volunteers also told in detail what they had eaten the previous day and agreed to use a sophisticated activity tracker for a week.

    The scientists then divided them randomly into groups. One group started a program of walking briskly or exercising five times a week until they burned 300 calories, which took most of them about 30 minutes. (The sessions were individualized)

    Over the course of the week, these volunteers burned an additional 1,500 calories with their exercise program.

    The other group started exercising for twice as long, burning 600 calories per session, or around 3,000 calories per week.

    The exercise program lasted 12 weeks. The researchers asked their volunteers not to change their diets or lifestyles during this time and to use the activity monitors for a few days.

    After four months, all returned to the laboratory and repeated the original tests.

    The results must have been disconcerting for some of them.

    Those men and women who had burned about 1,500 calories a week with exercise turned out to have lost little or no body fat, the tests showed. Some were heavier.

    But most of those who had walked the double was now thinner. Twelve of them had shed at least 5 percent of their body fat during the study.

    Then, the researchers used mathematical calculations, based on each person's fat loss (if applicable), to determine if and how much they had compensated for their exercise.

    The men and women in the group who had burned 1,500 calories a week with exercise proved to have compensated for nearly 950 of those calories, according to the figures.

    Interestingly, those in the other group had also compensated for some of the calories they had burned, and almost to the same extent as those who had exercised less, totaling about 1,000 calories per week, the calculations showed.

    But since they had spent 3,000 calories a week, they had ended up with a weekly deficit of around 2,000 calories from exercise and fat loss, the researchers concluded. The findings were published in the American Journal of Physiology-Regulatory, Integrative and Comparative Physiology.

    It was not entirely clear how the volunteers compensated, says Dr. Kyle Flack, an assistant professor at the University of Kentucky, who conducted the experiment as part of his graduate research.

    The resting metabolic rates of people have not changed during the study, he says, whatever group they have been in. Their activity monitors also showed little difference in how much or little they moved during the day.

    Then, the caloric compensation must have involved overeating, he says.

    But the volunteers did not believe it.

    "The memory of their food showed no difference" in the amount of food they reported at the beginning and end of the study, says Dr. Flack.

    "I think they just did not realize they were eating more," he says.

    There are probably also complicated interconnections between exercise, appetite, and people's relationships with foods that were not collected during this study and may affect diet and weight, he says. He hopes to study those problems in future studies.

    But already, the results of this experiment are encouraging, if you are cautious.

    "It looks like you can lose weight with exercise," says Dr. Flack.

    But success may require more effort from our body and will than we would expect, he adds.

    "Thirty minutes of exercise were not enough" in this study to overcome the natural urge to replace the calories we burn during a workout.

    "Sixty minutes of exercise was better," he says.

    But even then, people replaced about a third of the calories they consumed during exercise.

    "He still has to count calories and weigh portions" if he expects to use exercise to control his weight, he says.