Diet Without Exercise May be Harmful

In a new study, researchers show that people seeking to lose weight should select exercise rather than calorie restriction alone to accomplish their weight loss goals.

In a comparison of dieting verses exercise for weight loss, individuals in both groups lost weight (10 percent of their body weight) but the diet alone group lost some things they didn’t need to lose -- muscle mass, strength, and aerobic capacity.

The adults in the exercise group also lost a significant amount of body weight, 10 percent. More importantly, at the end of the study they had more muscle mass, strength, and aerobic capacity. Now armed with a revved-up metabolism from building and toning muscle, and increasing strength and aerobic capacity, study subjects in the exercise group have positioned their bodies to continue receiving the positive benefits of weight loss.

The lead researcher, Dr. Edward Weiss of Washington University School of Medicine in St. Louis, was quoted, "If push comes to shove and somebody wants to know if they should diet or exercise to lose weight, I would suggest exercise… Exercise-induced weight loss provides the additional benefit of improving physical performance capacity."
(Lower extremity muscle size and strength and aerobic capacity decrease with caloric restriction but not with exercise-induced weight loss. Weiss, 2007, Journal of Applied Physiology, 2007 Feb;102(2):634-40. Epub 2006 Nov 9).

Women Need to Know

In an earlier study, the Weiss research team demonstrated that weight loss with diet also caused a loss in bone density in all the wrong places. The researchers reported that clinically important sites of fracture took the direct hit from diet alone weight loss method. They concluded:

These data suggest that exercise should be an important component of a weight loss program to offset adverse effects of calorie restriction on bone.
(Bone mineral density response to caloric restriction-induced weight loss or exercise-induced weight loss: a randomized controlled trial. Weiss, 2006 Am J Clin Nutr. Dec 11-25;166(22):2502-10).

Even with this new study demonstrating the importance of exercise, diet remains important in the fitness strategy for people seeking to lose weight. Dr. Weiss said, “A critical requirement for exercise-induced weight loss is that food intake does not increase.” So don’t let these studies throw diet out-the-door.

Dieting can be an important component in this process, but adequate sleep and exercise play important roles in a sound weight loss strategy. Dieting without exercise can weaken bone at potential fracture sites in women, and will reduce muscle mass, strength, and aerobic capacity, which results in a sluggish metabolism.

Have a great day!

Phil Campbell, M.S., M.A.
Author, Ready, Set, Go! Synergy Fitness