Will physical activity help me lose weight?

Exercise alone won’t take off the pounds, but it’s critical to healthy weight loss.
Woman giving her trainer a high five

Weight loss is the main reason many of us exercise. While there are other reasons to get active (it improves health, gives us energy and it’s also fun), we as a society are fascinated by weight. Or to be more precise, we’re fascinated by fat.

Having excess body fat increases our risk for a number of conditions including certain cancers, heart disease and diabetes, not to mention stigma.

Let’s be realistic though: losing excess fat in the long-term is hard. It’s extremely hard.

The impact of our environment 

While we live in a society that views people with excess body fat as lazy, that’s really not the case. Our society promotes a lifestyle conducive to eating too much and being physically inactive. Some people have termed this the obesogenic environment, and it works against people trying to eat healthy and be active.

In spite of this environment, if we exercise we should be able to lose weight, right? Well, yes and no.

Any type of activity burns calories, whether we’re lifting weights or just walking downstairs to the kitchen. This is important, as the amount of fat on our body is related to the amount of calories we take in (through food) and burn off (through our metabolism and activity). However, it isn’t as simple as it sounds.

For many adults, we need somewhere between 1,500 and 2,000 calories to keep us alive at rest. This is our basal metabolic rate.

The recommended guideline for activity is 30 or more minutes per day on most days of the week. If you were to do brisk walking for this minimum time, you would only expend approximately 500 calories in a week. That’s about a medium apple or banana’s worth of calories per day, while a pound of fat is about 3,500 calories.

So while there are numerous benefits from even this little amount of activity, it won’t help us lose weight.

Compensating with calories 

There’s another factor that can make it hard to lose weight through exercise. It’s called compensation. Essentially, when we’ve done some physical activity we may compensate, either by being less active the rest of the day, or by eating more. We may even “reward” ourselves with food, counteracting the energy we used.

Lastly, here’s a complicating factor particular to weight bearing activities like walking, running, soccer, tennis and to some extent cycling: the less we weigh, the easier it is to move our bodies.

For example, let’s say a person’s regular exercise consists of a two kilometre walking route, and over a few weeks that person loses two pounds. As a result of weighing less, walking that same two kilometres at the same speed will actually use fewer calories.

This means that as we lose weight, we need to become more active to lose more weight. 

How exercise helps

So even though exercise itself is not very effective in helping us lose weight, it still has a very important role within a weight-loss regimen. While the cornerstone for weight loss is alterations in diet, when we lose weight by diet alone, this commonly includes a loss of muscle mass as well as fat.

This loss in muscle mass is detrimental to our health. Adding exercise to a weight-loss diet helps to prevent any loss in muscle mass and ensures that whatever weight is lost comes from body fat.

Overall, the best way to lose body fat is through a combination of both diet and exercise.

And remember, even if we don’t lose a single pound, exercising and being active has so many other benefits to reduce our risk for diabetes, cancer, heart disease, osteoporosis and stress, and to improve our mental well-being.

Dr. Scott LearDr. Scott Lear is a leading researcher in the prevention and management of heart disease. He holds the Pfizer/Heart and Stroke Foundation Chair in Cardiovascular Prevention Research at St. Paul’s Hospital in Vancouver, and he is a professor in the faculty of health sciences and the department of biomedical physiology and kinesiology at Simon Fraser University. Dr. Lear also lives with heart disease himself. Follow his blog at drscottlear.com.