Medical Compass: How much exercise should we get?

Medical Compass: How much exercise should we get?

Exercising 30 minutes four to five times a week is best. Stock photo
It is possible to overdo exercise for weight loss purposes

By David Dunaief, M.D.

Dr. David Dunaief

When we make a New Year’s resolution to exercise regularly, the goal is often either to change body composition, to lose weight, or at least to maintain weight. How much exercise is best for these purposes? It is a hotly debated topic. You would think the answer would be straightforward, since exercise helps us prevent and resolve a great many diseases.

At the same time, we hope exercise impacts our weight. Does it? It is important to manage our expectations, before we start exercising. There are some intriguing studies that address whether exercise has an impact on weight management. The short answer is yes; however, not always in ways we might expect.

Then the questions become: What type of exercise should we be doing? How frequently and for how long? Let’s look at the evidence.

Duration

It makes sense that the more we exercise to lose weight, the better, or at least that is what we thought. In a small randomized controlled trial (RCT), the gold standard of studies, results showed that the moderate group in terms of duration saw the most benefit for weight loss (1). 

There were three groups in the study — a sedentary group (low), a group that did 30 minutes per day of aerobic exercise (moderate) and a group that did 60 minutes per day of aerobic exercise (high).

Perhaps obviously, the sedentary group did not see a change in weight. Surprisingly, though, the group that did 30 minutes of exercise per day experienced not only significantly more weight loss than the sedentary group, but also more than the 60-minute exercise group. The aerobic exercises involved biking, jogging or other perspiring activities. These were healthy young men that were overweight, but not obese, and the study duration was three months.

The authors surmise that the reason for these results is that the moderate group may have garnered more energy and moved around more during the remainder of the day, as sensors showed. The highest exercise group was sedentary through most of the rest of day, probably due to fatigue. Also, it seemed that the highest exercise group ate more than the moderate group, though the difference was not statistically significant. While this study is of impressive quality, it is small and of short duration. Nonetheless, its results are encouraging.

Postmenopausal women

As a group, postmenopausal women have considerable difficulty losing weight and maintaining weight loss. In a secondary analysis of a randomized controlled trial, there were three aerobic exercise groups differentiated by the number of kcal/kg per week they burned: 4, 8 and 12 (2). All of the groups saw significant reductions in waist circumference. Interestingly, however, a greater number of steps per day outside of the training, measured by pedometer, were primarily responsible for improved waistline circumference, regardless of the intensity of the workouts.

But it gets more intriguing, because the group that exercised with the lowest intensity was the only one to see significant weight loss. More is not always better, and in the case of exercise for weight loss, less may be more. This study reinforces the suppositions made by the authors of the previous men’s study: We should exercise to a point where it is energy inducing and not beyond.

Premenopausal women

Not to ignore younger women, those who were premenopausal also saw a significant benefit with weight maintenance and exercise after having intentionally lost weight.

In a prospective (forward-looking) study, young women who did at least 30 minutes of exercise four to five days per week were significantly less likely to regain weight that they had lost, compared to those who were sedentary after losing weight (3).

Some of the strengths of this study were its substantially long six-year follow-up period and its large size, involving over 4,000 women between the ages of 26 and 45. Running and jogging were more impactful in preventing weight gain than walking with alacrity. However, all forms of exercise were superior to the sedentary group.

Aerobic exercise and resistance training

In another RCT with 119 overweight or obese adults, aerobic exercise four to five times a week for about 30 minutes each was most effective for weight loss and fat reduction, while resistance training added lean body mass. Lean body mass is very important. It does not cause weight reduction, but rather increased fitness (4).

With weight loss, it’s important to delineate between thin and fit. Fitness includes a body composition of decreased body fat and increased lean muscle mass. To help achieve fit level, it’s probably best to have a combination of aerobic and anaerobic exercise (resistance training). Both contribute to achieving this goal.

In conclusion, exercise can play a significant role in weight, whether with weight reduction, weight maintenance or increasing lean body mass. It appears that 30 minutes of exercise four to five times a week is best. Longer is not necessarily better.

What is most important, however, is to exercise to the point where it energizes you, but doesn’t cause fatigue. This is because it is important not to be sedentary the rest of the day, but to remain active. We should also include a complete package of lifestyle modifications in general — diet, exercise and stress reduction — to get the most compelling results.

References:

(1) Am J Physiol Regul Integr Comp Physiol. 2012 Sep 15;303(6):R571-R579. (2) Am J Prev Med. 2012;43(6):629-635. (3) Obesity 2010;18(1):167-174. (4) J Appl Physiol. 2012 Dec;113(12):1831-1837.

Dr. Dunaief is a speaker, author and local lifestyle medicine physician focusing on the integration of medicine, nutrition, fitness and stress management. For further information, visit www.medicalcompassmd.com or consult your personal physician. 

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