Physical activity and weight loss

Learn about the principles of energy balance, calories and how physical activity can help maintain or reduce body weight.

Man exercising by running up stone steps.
Of the three basic caloric expenditure factors, we have the most control over the thermic effect of physical activity.

It’s summer, and no matter where you look, you see advertisements about weight loss. Whether it’s an ad is for a new fad diet or some secret weight loss herb that has been known to civilization “X” for thousands of years. Where do you begin and what should you believe?

Weight loss versus fat loss

First, weight loss and fat loss are not the same thing. Fat loss refers to losses in adipose tissue (body fat) specifically, while weight loss is referring specifically to a loss of overall body weight. Because body weight includes everything that makes up your body, weight loss can include loss of adipose tissue but can also include losses in other bodily tissues (e.g. muscle tissue) and fluids.

What are calories?

The principles behind weight loss are actually much simpler than popular media sources want us to believe. To understand this, we need to know what a calorie actually is. Calories (actually kilocalories) are the amount of energy a food or beverage provides. To effectively lose weight, you need to be in a caloric deficit, which means you are expending (“burning”) more calories than you are consuming (from eating foods and drinking beverages). You can be in a caloric deficit in a few different ways: eating less calories and performing more physical activity; eating the same amount of calories and performing more physical activity; or eating less calories while performing the same amount of physical activity. Can it really be that simple? Yes, and likely cheaper than what some advertisements want you to believe.

Calories consumed versus calories expended

The food and beverages we eat and drink are made up of either (or a combination of) protein, carbohydrates, fat and alcohol. Each of these provide a different amount of energy/calories per gram.

  • One gram of protein = 4 calories
  • One gram of carbohydrates = 4 calories
  • One gram of fat = 9 calories
  • One gram of alcohol = 7 calories

You may have heard that not all calories are the same, which is true to an extent. Depending on the source, calories are absorbed and metabolized differently. However, if you are consuming more calories than you are expending for a period of time regardless of the type of food you are eating, you will be in a state of caloric surplus and will gain weight. Likewise, if you are expending more calories than you are eating, you will lose weight.

The three biggest factors that affect caloric expenditure are basal metabolic rate, the thermic effect of food and the thermic effect of physical activity. Basal metabolic rate (which includes basic cellular function processes) represents about 60-80 percent of an individual’s daily caloric expenditure, with the percentage being lower in more active individuals. The thermic effect of food contributes about 5-10 percent of one’s daily caloric expenditure, and the remaining caloric expenditure is due to the thermic effect of physical activity. Of the three basic caloric expenditure factors, we have the most control over the thermic effect of physical activity. 

Physical activity and weight loss

So where to begin? If you are not currently physically active, I recommend you adopt an exercise regime. This is a great first step to increasing the amount of calories you will burn each day. Remember to start slow. For further information about physical activity recommendations refer to my previous article on general physical activity recommendations.

If you are currently meeting physical activity recommendations, you can also alter your current training program to expend more calories. This could be as simple as increasing the number of sessions you go to the gym each week or how far or how fast you are jogging. Challenge yourself to think of fun, simple ways to incorporate physical activity into your everyday life.

The type of activity, intensity of the activity, and duration will dictate how many calories are “burned.” Refer to some of my previous articles about strength and cardiovascular training for more information. 

So how do your work out how many calories you need so you can avoid a caloric surplus and be in a caloric deficit? Also, how can you eat the right amount of food to minimize how much muscle tissue you could lose from being in caloric deficit? The answer to these questions is different for each of us. I highly recommend you seek out a registered dietician for nutritional consulting. These individuals are trained experts in the field of nutrition with degree(s) from accredited dietetics programs and can evaluate someone’s current dietary pattern and make suggestions. Additionally, they are a great resource to help you make sense of all the misinformation surrounding fad diets. For further information the International Society of Sports Nutrition has a great evidence-based position statement on different dietary patterns and weight loss.

Beyond the gym

Increasing your caloric expenditure by being more physically active does not necessarily mean you have to join a gym. You can also perform other physical activities such as joining a softball league, taking a mile walk each night with a significant other, taking the stairs instead of the elevator, walking the dog, gardening and playing with your kids or grandkids. The overall idea is you are trying to incorporate more activity into your day-to-day.


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