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Exercise and Obesity

Author: Stan Reents, PharmD
Original Posting: 05/06/2007 09:06 AM
Last Revision: 01/15/2016 08:00 AM

Health statistics show that one-third of Americans are overweight (BMI > 25) and another third are obese (BMI > 30).

The media and the medical profession have identified obesity as not only a personal health issue, but as an impending medical crisis (Manson JE, et al. 2004; Vastag B. 2004). While scientific evidence shows that obesity does have a genetic component, lifestyle factors are probably more important. So, if that's true, then obesity should be preventable and reversible.


  • regular consumption of fruits, vegetables, and whole grains
  • avoidance of high-fat foods
  • regular exercise





So, does exercise work, or not? The short answer to this question is: "it depends."

Of course exercise burns calories, and, it's also true that if more calories are burned than consumed, then body weight will decrease. Even when taken to the extreme, these relationships apply. Consider, for example, Tour de France cyclists: despite an intake of 6000-7000 calories per day, they still lose weight during the 21-day race.



The most important explanation why exercise isn't effective for many people trying to lose weight is that exercise represents only a small percentage of the calories burned in any 24-hr period. Even a full hour of vigorous exercise in these people constitutes only about 10-30% of the total calories they burn up in a given 24-hr period. Contrast that to the Tour de France athlete who cycles at a furious pace for 6 solid hours, burning up as much as 9000 calories in a single day.

For Most People, a Single Exercise Session Just Doesn't Burn Enough Calories

Most people burn way more calories during "routine daily activities" (vacuuming, raking, sweeping, washing the car, etc.) than they would during a typical exercise session:

• routine daily activities 65 - 75% of the day's total
and prolonged
• digestion 5 - 10%








A simple rule-of-thumb to remember is this:

An excess of 500 calories per day, every day for 7 days, will lead to 1-lb of weight gain per week.

That's how easy it is to gain weight. Stop and think of how many calories are in an average dessert at a restaurant. An excess of 500 calories is not going to make you "feel full." Unless you increased your exercise or physical activity on a day that you consumed excess calories, then you may have exceeded that magical 500 calories per day rule.

Fortunately, the reverse is also true:


OK, weight loss is not quite THAT simple but, still, this is a helpful rule to keep in mind when you dine out. (Remember the Consumer Reports survey above regarding food choices and portion sizes?...)


Exercise does work. Here are some positive results:


These are very impressive results, but very few people are willing to run 95-km per week. Fortunately, it turns out that exercise doesn't have to be punishing to produce effective weight loss:






Resistance exercise strengthens the bones and maintains muscular strength. It doesn't take much resistance to have a positive effect on bone density: In a study of squash players, simply swinging a light-weight squash racquet produced a noticeable increase in the density of the bones of the dominant arm. Muscle strength is improved by any form of resistance-training (eg., weight-lifting, push-ups, sit-ups, squats, working-out with rubber bands, etc.), but even walking will increase muscle strength in the muscles of the legs and back.

In fact, if there ever was a "magic bullet" in medicine, it would be exercise. William Roberts, MD, then Editor-in-Chief of the American Journal of Cardiology once referred to exercise as:


That was back in 1984 (Roberts WC. 1984). Today, we know that, in addition to all those properties, exercise is also beneficial for cancer, dementia and mental health, osteoporosis, sexual dysfunction, and many other medical problems.



In 1995, the American College of Sports Medicine (ACSM) recommended at least 150 minutes of exercise per week for otherwise healthy adults (Pate RR, et al. 1995). That translates to 30 minutes per day on 5 days each week. But subsequent research suggests that 150 minutes per week is not enough for weight loss. Two hundred minutes per week (or more) will not only achieve a greater weight loss, but, more importantly, will do a better job of keeping that weight off (Jakicic J, et al. 1999).


> 195 minutes / week 4.2%
136 - 195 minutes / week 2.4%
< 136 minutes / week 0.6%



People over age 65 rarely follow diet and exercise programs for weight loss. Obesity is increasing among the senior population just as it is for other age groups. This results in significant health and lifestyle concerns.



1) Aim to exercise three days per week initially. Gradually work up to five days per week, varying the program on alternating days to prevent boredom.

2) The higher the level of obesity, the more difficult it will be to exercise. Start with 30 minutes of exercise broken down into 10 minutes of cardiovascular activity (eg., walking on a treadmill, stationary cycling), 10 minutes of weight-lifting using 5-10-pound dumbbells, and 10 minutes of flexibility exercises. Increase the duration of each phase of exercise as you become more capable and comfortable with the program. Rest as necessary to prevent premature fatigue.



5) Do not be too concerned about your weight during the early stages of the program. The primary goal is regular exercise.

Hiring a personal trainer, at least during the first few exercise sessions, is highly recommended.





• Walk or bike to the store whenever possible


• Buy a pedometer and wear it daily




Daily Physical Activity


• Park at the far end of the parking lot

• Take the stairs, not the elevator or escalator


• Mow your lawn with a push-mower

• If you have a sedentary job, stand up and move around hourly. Buy an activity tracker and wear it daily



• Exercise at least 5 days per week for a total of at least 150 minutes per week. If possible, exercise 200 minutes per week. Even if no weight is lost, you will be obtaining health benefits (lower blood pressure, for example). Also, it's possible that you are losing fat but this trend is disguised because you are simultaneously adding muscle.

• Exercise does not have to be intense to burn calories. Walking has been shown to be effective. Slow bicycling, however, because most of your body weight is supported, is probably not very effective.



An excellent exercise book for consumers is ACSM Fitness Book (Human Kinetics, $16.95). It contains charts for body mass index (BMI) and waist-to-hip ratio.

Readers may also be interested in these reviews:

Use our Exercise Calorie Converter to determine how much exercise is required to burn off the calories in menu items from specific restaurants. We also offer an app that you can install on your mobile device: Mobile Apps



















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