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Can you exercise your way to weight loss?

August 11, 2018 (updated July 2o2o)

As a personal trainer, I have a lot of discussion with my clients about weight loss. Whenever I first meet a new client and ask them to tell me what their goals are, weight loss is invariably high on the list.

And I’m very careful to explain to them the misconceptions about an exercise program and meaningful weight loss.

I want them to be positive about the benefits of a regular exercise program but I also want them to have a realistic expectation of what they will achieve with that program.

Weight loss, is simply, about expending more calories than you consume, known as a calorie deficit. And you need a deficit of about 3500 calories to lose 1 lb of body weight. Here is the first misconception. It is very difficult to burn a lot of calories with exercise alone, regardless of the intensity.

The first step in starting a weight loss program is to calculate both average total daily calorie intake and average daily calorie use, known as TDEE or Total Daily Energy Expenditure.

TDEE consists of three parts. Firstly there is your RMR or Resting Metabolic Rate. This is the number of calories required to maintain basic bodily functions such as breathing, circulation and digestion. This rate is influenced by age, body composition and diet.

Secondly there is your occupational activity level which is determined by how active you are apart from an exercise program. This can range from sedentary to very active.

Finally there are the calories burned during an exercise program. All these factors may be determined from gathering data and then using various formulas.

Calorie intake may be determined by several methods such as keeping a food diary, or using one of the many available apps for this purpose.

Now that you have both numbers you can calculate your average daily calorie deficit. So for example if calorie intake is 2000 and TDEE is 2500, then your deficit is 500. If your weight loss goal is, say 10 lb, then you would achieve that by maintaining the deficit for 10 weeks.

Note that the deficit can also be achieved by decreasing intake, increasing TDEE or both. So your deficit could be achieved by decreasing you intake by 250 calories or increasing your TDEE (through exercise) by 250 calories.

The biggest impact that regular exercise has on this equation is to increase your RMR and thus increase your TDEE.  However it is important to remember that most exercise sessions will only contribute 10-15% of TDEE.  Aerobic exercise will increase TDEE directly while weight training will increase RMR.

Once you have reached your target weight, equalizing intake and TDEE will maintain that weight.

Some general principles of a weight loss/management program:

  • Weight loss should be gradual – no more than 2 lb/week
  • Calorie intake should be at least 1000 per day (to maintain RMR)
  • A calorie deficit should never exceed 900/day.

Weight loss is seldom steady or linear, because there are so many different factors at work. Awareness, consistency and help from a personal trainer will all help you achieve your goal.