How Strength Training Can Help You Lose Body Fat

Conventional knowledge tells us that aerobic exercise is the ticket to weight loss. Ask any trainer and they will tell you they’ve had clients who insist on doing cardio to lose weight before starting a strength training program.  

Unfortunately, this approach usually leads to disappointing returns due to several factors:  

Many people find aerobic exercise stimulates appetite. They end up eating more calories, negating the calorie deficit they created from training.  

People who do manage to create an energy deficit will end up losing a lot of muscle in addition to fat and their metabolic rate drops.  

The end result in both cases is stalled weight loss and rebound weight gain over the long run.  

A better approach is to combine strength training with cardio and a focus on diet. This exercise combination will help maximize total energy expenditure by these four powerful mechanisms:  

1) It maintains muscle to keep your metabolic rate cranking 

2) It increase levels of catecholamine hormones that stimulate energy expenditure 

3) It increase the use of glucose and fat burning in the body 

4) It improves mobility and reduces joint pain allowing people to be more active during the day 

A recent study using an elderly population at high risk of losing muscle illustrates the superiority of combining cardio and strength training. Overweight volunteers with an average age of 70 were randomized into one of four groups:  

A Control group that made no changes. 

An Aerobic group that did 50 minutes of cardiovascular exercise three days a week and participated in a weight management program that provided an energy deficit of 500 to 750 calories a day.  

A Resistance Training group that did 50 minutes of strength training exercises three days a week and participated in the weight management program that provided an energy deficit of 500 to 750 calories a day. 

A Combined Training group that did 40 minutes of cardio and 40 minutes of strength training three days a week and participated in the weight management program that provided an energy deficit of 500 to 750 calories a day. 

Participants were asked to consume 1 g/kg of protein a day as well as 1,500 mg of calcium and 1,000 IU of vitamin D daily.  

Results showed that all three intervention groups lost about the same amount of weight with the Aerobic group losing 9 kg and the Combo and the Resistance Training groups both losing 8.5 kg. There was a significant difference in terms of the amount of fat and muscle lost:  

The Aerobic group lost 2.7 kg of lean mass and 6.3 kg of fat.  

The Resistance Training group lost 1 kg of lean mass and 7.3 kg of fat.  

The Combo group lost 1.7 kg of lean mass and 7 kg of fat mass.  

Scores on a physical performance test showed that the Combination group improved significantly more than the other two exercise groups, increasing performance by 22 percent compared to a 15 percent boost in both the Aerobic and the Resistance Training groups. Peak oxygen consumption, a measure of aerobic capacity, improved a similar amount (about 18 percent) in the Aerobic and Combination groups. The Resistance group had a small but significant improvement in peak oxygen consumption of 7 percent.  

Scores on a quality of life test improved the most in the Combination group, increasing by 24 percent, compared to a 14 percent increase in the Aerobic group and a 17 percent increase in the Resistance Training group.  

Researchers concluded that older, overweight adults are well suited to properly designed training programs and that the combination of resistance and aerobic training translates into greater quality of life and improvements in physical function than either done alone.  

This study adds to a body of literature showing benefits from including strength training in a weight loss program, regardless if it is combined with cardio, in multiple populations. For example, a 2015 study of young women who either dieted, dieted and did aerobic cardio, or dieted and did strength training found that the women who lifted weights increased lean mass by 0.3 kg, while losing 12 kg of body fat. A group that did aerobic cardio lost 0.5 kg lean mass in addition to losing 11.9 kg of fat mass.  

This study also tested how the changes in body composition impacted energy expenditure. First, they looked at resting energy expenditure, or the number of calories the burned at rest daily. The women who lifted weights increased their energy expenditure by 63 calories, whereas the aerobic group decreased daily calories burned by 63.  

Next they assessed spontaneous energy expenditure, which is the number of calories burned in non-exercise activity over the course of the day (stuff like walking around your house, working, doing chores, or driving a car). The women in the strength training group increased this marker of energy expenditure by 51 calories whereas the aerobic group decreased by 87 calories. Researchers believe that the women who lifted weight had better mobility and they improved how they felt about their bodies, which allowed them to be more active during the day.  

Take Aways:  

Both cardio and strength training can help you lose weight. The best approach for maximal fat loss is to combine the two in a well-designed training program so that you maintain muscle and strip off fat.  

If you only have time for one training mode, it’s worth doing strength training, especially if you are older or have low muscle mass to begin with because this will set you up for longer term success. 

Focusing on nutrition is important. For fat loss, you need to create a calorie deficit—an endeavor that is much easier if you are eating whole foods and getting adequate protein.  

References: 

Hunter, G., et al. Exercise Training and Energy Expenditure following Weight Loss. Medicine and Science Sports and Exercise. 2015. 47(9): 1950-1957.  

Villareal, D. T., et al. Aerobic or Resistance Exercise, or Both, in Dieting Obese Older Adults. The New England Journal of Medicine. 2017. 376(20), 1943–1955.