Last month I posted Tony Leyland’s article on strength and muscle size discussing neuromuscular efficiency and gains in muscle size. Here in Leylands’s follow up he goes on to discuss the evidence supporting these views.

Strength, Muscle, Fat and Body Composition

In my last article (“Strength and Muscle Size”) I talked about how we develop strength: namely improvements in neuromuscular efficiency and gain in muscle size. I noted that young males, who will have higher levels of testosterone, would tend to increase strength by building bigger muscles, whereas females and older males will tend to rely more on improvements in neuromuscular efficiency.  In this article I want to discuss some of the direct evidence to back up this view.

Ballor, et.al, (1988) conducted an 8-week program with 40 obese women. The subjects were assigned to one of four groups (control, diet only, weight training only, diet and weight training). The group that weight-trained and dieted lost more fat than the groups that either dieted or weight-trained alone. This study demonstrates that weight training can maintain (or increase) lean mass even while dieting. The results of this study are show below.

Control Diet Weight Training Weight Training & Diet
Weight (kg) -0.38 -4.47 0.45 -3.89
Fat (kg) -0.07 -3.56 -0.62 -4.32
Lean mass (kg) -0.31 -0.91 1.07 0.43

The bar chart below shows the table results. Some people like pictures better than numbers! Note the units are kilograms not pounds.

This information can be accessed on www.ExRx.net, which is an excellent site that is accurate but does not get too scientific in the presentation of fitness & health information.

http://www.exrx.net/FatLoss/WTCalLBWStudy.html

A very important point to highlight from this study is the loss of muscle mass that occurred with the diet only approach. If the reason you are working out is to improve your health then the message is clear that diet only will not serve you well. Health would include being able to function independently later in life; so dieting and loosing muscle mass is not a good strategy to keep you independent as you age. However, if your only concern is appearance and what the weight scale says you may be beyond hope….but keep reading anyway!

So diet alone doesn’t look ideal but what about diet and low-intensity aerobic exercise? Westcott (1991) trained 72 overweight individuals in one of two ways: 30 minutes of endurance exercise on a stationary cycle or 15 minutes of exercise on the stationary cycle plus an additional 15 minutes on weight resistant exercises. At the conclusion of the study, the “endurance only” group lost a total of 3.5 lbs.; 3 lbs. of which was fat and a half-pound was muscle loss. On the other hand, the “endurance and weight resistive” group lost 8 lbs. with an actual fat loss of 10 lbs. and an increase of 2 lbs. of lean body weight. So adding in weight training helps you improve your body composition more effectively than aerobic endurance work alone. You can see the graphs at the link below.

http://www.exrx.net/FatLoss/WT&End.html

Evidence that resistance weight training combined with endurance training improves fat loss is also available in the literature.

http://www.exrx.net/FatLoss/DietExStudy.html

As is evidence that high-intensity exercise is the best way to lose fat.

http://www.exrx.net/FatLoss/HIITvsET.html

Regardless of total body weight loss, if you loose body fat and gain muscle then you will “trim down” even if your weight remains constant. Muscle is about 18% denser than fat (muscle density = 1.06 g/ml and fat density = 0.9 g/ml). So if you stay the same weight but loose 5 pounds of fat and gain 5 pounds of muscle you get trimmer. The picture below shows one pound of muscle and one pound of fat.

You can go on-line and find many anecdotal testaments to the effect of correct exercise on body size (not weight). For example some females have dropped from a size twelve to a size eight – while gaining six pounds. I cannot attest to the exact numbers because as stated these claims are anecdotal. However, I have already discussed studies that have shown resistance training can lead to loss of body fat and gain in muscle. And as fat is less dense than muscle many women trim down in terms of dimensions while increasing strength even if they do not loose weight.

So the take home message is not to worry about the scales. Look at your performance numbers, look in the mirror and perhaps measure some circumferences.

Do not measure your fitness progress by using your bathroom scale!

Tony Leyland is Senior Lecturer at the School of Kinesiology, Simon Fraser University, Vancouver, British Columbia. He has taught at the university level for 26 years and has been heavily involved in competitive sports such as soccer, tennis, squash, and rugby as both an athlete and a coach for over 40 years. He is a professional member of the National Strength and Conditioning Association, a Canadian National B-licensed soccer coach, and a level-1 CrossFit trainer. He can be reached at leyland@sfu.ca.