Exercise for Weight Loss

Definition of Exercise

Physical exercise can be defined as deliberate muscular activity (work) performed regularly and of sufficient intensity and duration to maintain or improve health. Not coincidentally, exercise almost always improves rate, total amount and long-term success of weight loss (more specifically of body composition). Along with dietary change, exercise is one of the two major facets of every sensible weight loss plan.


Given the extreme importance of exercise, I will devote a lot of attention to it here. I'll try to tackle most of the issues that I have encountered over twenty years in bariatric medicine.

Exercise is the MAIN control we have over calorie output... or is it?

We can modify calorie intake through dietary change, and we can slightly increase the thermic effect of food (TEF) through macronutrient choices, but our primary control over how many calories we burn lies with exercise. This means, of course, that with enough exercise we could eat anything and still lose weight. This is rarely practical however since it often requires upwards of 2 hours of exercise daily. More appropriately, exercise can allow us to enjoy a wider variety of foods with less concern for strict control. In other words, reasonable dietary change combined with moderate regular exercise makes weight loss a whole lot easier. Obviously it can also make weight loss happen faster, but where exercise REALLY makes all the difference is with weight maintenance.

Does Exercise Even Work for Weight Loss?

Unfortunately, it may not. I personally have met thousands of patients who have spent lots of money and time on exercise to no avail. As we'll see shortly, this might be because exercise slows (that's right SLOWS) metabolism. It appears that the human body may compensate for moderate exercise by burning fewer calories elsewhere. More on this later.

Exercise, more than anything else you do, will determine long-term success in weight loss:

I often tell patients "you can lose weight even if you don't exercise, but unless you start doing it, you won't keep it off". It's generally about that simple. Time and again, people who exercise live thinner and healthier lives than people who do not. We'll explore why this is true as we progress through this chapter.

Exercise and Calories

Exercise involves muscular contraction used to perform physical work. To put it another way, exercise requires energy. The energy required for exercise comes from breaking the chemical bonds of substances stored in the body. Generally these substances are either glucose (sugar) or fat, but in any case, breaking these substances down involves "burning" energy or calories. Exercise is work and work requires energy. Exercise burns calories.


The word "exercise" means different things to different people. For a professional athlete,exercise may involve several hours of high intensity training nearly daily. For a formerly sedentary sixty year old man with diabetes and obesity, it may mean fifteen minutes of walking just a few times per week. Advice that would apply to the athlete would be dangerous for the diabetic. 

To be effective, and most important, to avoid injury and burnout, exercise needs to be specifically tailored to each person in a manner that accounts for health, physical condition, age, gender, goals, values, culture, income, time and weight.