Men who do strength training keep their fat percentage lower in the long term than men who run, cycle or do other aerobic exercise. Epidemiologists at the University of Harvard came to this conclusion after following 10,500 men for 12 years.
Strength training and body fat
At first glance you’d think that aerobic forms of exercise such as running, cycling and rowing would offer better protection against building up excess fat than strength sports do. A weights workout burns a couple of hundred kilocalories at most, while an hour of intensive aerobic training will easily help you burn eight hundred kilocalories.
On the other hand though: after the age of thirty you lose a little bit of muscle mass each year. Because every kilogram of muscle mass you lose also lowers your daily calorie burning by a couple of dozen kilocalories, the older you are, the more easily you put on weight. You can stop this process by doing strength training. If you train really hard and eat enough protein, you can even build up more muscle mass as you age. Aerobic forms of exercise contribute little to building up more muscle mass.
The researchers used data on over 10,000 healthy men that had been gathered between 1996 and 2008 in the Health Professionals Follow-Up Study, including information on how the waist measurement of the participants had changed over the study period. When the study began in 1986, the participants were aged between 40-75.
“Because aging is associated with the loss of skeletal muscle mass, relying on body weight is insufficient for the study of healthy aging”, explained Rania Mekary, the first author of the study, in a press release. [harvard.edu December 22, 2014] “Measuring waist circumference is a better indicator of healthy body composition among older adults.”
The researchers divided the men up according to the amount of exercise they got. First the researchers looked at the amount of moderate to vigorous aerobic activity [MVAA] the men got daily. The norm is at least half an hour a day of this type of exercise.
Then the researchers looked at the number of minutes a day the men devoted to strength training.
Strength training offered more protection against a growing waist circumference than moderate to vigorous aerobic activity did, according to the figure below.
During the period that the researchers monitored the men, their waist measurement increased by an average of 6.6 cm. Strength training reduces this increase by 3 cm. According to this study, that happens regardless of whether you adhere to the norm for moderate to vigorous aerobic activity or not.
The researchers even calculated that if the participants had done 20 minutes of strength training daily during the 12 years of the study instead of 30 minutes of aerobic activity, they would have lost another 0.34 cm from their waist measurement. It would have been even better if they had done 20 minutes strength training a day instead of of watching TV for 30 minutes: that would have resulted in a reduction of 0.76 cm on the waist measurement.
The leader of the project, Frank Hu, emphasised in a press release [harvard.edu December 22, 2014] that the study does not show that aerobic forms of exercise are therefore no longer necessary. Aerobic exercise has positive effects on the cardiovascular system that strength training does not have.
“This study underscores the importance of weight training in reducing abdominal obesity, especially among the elderly”, said Hu. “To maintain a healthy weight and waistline, it is critical to incorporate weight training with aerobic exercise.”
Weight training, aerobic physical activities, and long-term waist circumference change in men.
Findings on weight training and waist circumference (WC) change are controversial. This study examined prospectively whether weight training, moderate to vigorous aerobic activity (MVAA), and replacement of one activity for another were associated with favorable changes in WC and body weight (BW).
Physical activity, WC, and BW were reported in 1996 and 2008 in a cohort of 10,500 healthy U.S. men in the Health Professionals Follow-up Study. Multiple linear regression models (partition/substitution) to assess these associations were used.
After adjusting for potential confounders, a significant inverse dose-response relationship between weight training and WC change (P-trend?<0.001) was observed. Less age-associated WC increase was seen with a 20-min/day activity increase; this benefit was significantly stronger for weight training (-0.67 cm, 95% CI -0.93, -0.41) than for MVAA (-0.33 cm, 95% CI -0.40, -0.27), other activities (-0.16 cm, 95% CI -0.28, -0.03), or TV watching (0.08 cm, 95% CI 0.05, 0.12). Substituting 20 min/day of weight training for any other discretionary activity had the strongest inverse association with WC change. MVAA had the strongest inverse association with BW change (-0.23 kg, 95% CI -0.29, -0.17).
Among various activities, weight training had the strongest association with less WC increase. Studies on frequency/volume of weight training and WC change are warranted.
©2014 The Obesity Society.
PMID: 25530447 PMCID: PMC4310793 DOI: 10.1002/oby.20949 [PubMed – indexed for MEDLINE]