When people look to lose weight, many turn to exercise as the solution. And why not? Exercise burns calories, which in turn could come from fat and result in weight loss. And as the proportion of people who are overweight or who have obesity has climbed in all parts of the world, focus on weight loss continues to be strong. But while exercise should be part of any weight loss or maintenance program, it’s not because of the calories it burns.
Exercise and Weight Loss
The reality is, exercise itself does little to help with weight loss. It’s true people who are active tend to be less likely to have obesity. But this could also be due, in part, to people who are overweight being less likely to be active. Having obesity is associated with a number of mobility limitations, which can make activity uncomfortable and even painful. People with obesity who have faced weight stigma are also more likely to avoid exercise and have less of a desire to exercise in public.
Studies on exercise alone on weight loss have provided modest results. Overweight men who underwent 16 months of supervised exercise five times per week had an average loss of 10 pounds. However, less than half of the participants completed the program and there was no weight change in women. And while more exercise can result in more weight loss, it’s not necessarily linear. On average, a year of exercise may result in a weight loss of 3.5 pounds.
While these small amounts in fat loss may result in improved risk factors and better health, it’s far below what people expect. It’s also important to note, these are averages and not everyone will respond the same. Within the same study, some people may lose much more weight, while others may lose none, or even gain weight.
The Truth About Exercise and Calories
So why are these results so poor? Part of this is due to how much, or how little, calories exercise actually uses. Simplifying a complex issue, weight gain (or more precisely, fat gain) occurs when your body takes in more calories than it can burn. We burn calories through our body’s metabolism, the thermic effect of food and any activity. The main contributor is our body’s metabolism. Most people use 1300 to 1800 calories per day just to keep the body going. Digesting food adds only a small amount.
Then there’s our activity. Much of most people’s day is spent in sedentary and activities of low intensity, which is negligible in terms of calorie requirements. That leaves exercise, or activity for the purpose of being active. However, meeting the minimal exercise recommendations of 150 minutes per week of moderate activity translates to about 500 calories, or 100 to 120 calories per 30 minutes of brisk walking. About the same amount of calories as an apple.
Another possibility is what’s called compensation. This can be in two types; compensating by being less active the rest of the day, or compensating by increasing our food intake. In some instances, we may ‘reward’ ourselves with food for doing exercise, and thereby counteracting the energy used to exercise by eating more.
First off, being active does burn calories. This isn’t in doubt. It’s just not as much as we assume. But in addition, we’ve also been bombarded with programs, promotions and marketing indicating exercise is the path to weight loss.
Much of this comes from segments of the food industry that blame rising rates of obesity on a lack of physical activity. Not on food intake. The food industry does this to direct attention away from criticizing their high-calorie, nutrient poor foods. This can come in the subtle form of sponsoring and supporting physical activity campaigns to more directly pointing the finger at physical inactivity as a former Pepsi CEO did. And Coca-Cola even funded scientists to purposely pinpoint lack of activity as the cause of obesity.
Why Exercise is Important to Weight Loss
Despite this, weight loss programs which incorporate exercise tend to produce better results than those that don’t. Compared to diet or exercise alone, the combination of the two generally results in greater weight loss, but more importantly greater fat loss. And in the long-term, diet plus exercise programs are more effective at sustaining the initial weight loss.
The added benefit of exercise to a weight loss program is likely the result of a number of reasons. First, people who exercise tend to also engage in other healthy behaviours. People initiating an exercise program also reduced their dietary caloric intake. This occurred without a specific dietary intervention. Exercise also decreased the preference for a high-fat diet in mice that aligned with neurological changes. These changes may make it easier to stick to one’s weight loss diet.
In addition, there is some evidence to suggest exercise can blunt the decrease in resting metabolic rate that occurs with diet alone. With diet, resting metabolic rate has been observed to decrease and may be the body’s way to resisting weight loss. Exercise, on the other hand, has been shown to increase resting metabolic rate. However, not all studies are in agreement and the effect of exercise on resting metabolic rate may be greater from resistance training than aerobic training.
Lastly, the benefits of exercise extend beyond just burning calories and aiding in weight loss. These include benefits to physical and mental wellbeing. Many of which aren’t achievable through dietary means.
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