To fight that fat gut, what's better? More weight training or more cardio? Let's see what science says.
Middle Age & Belly Fat
As men age, they tend to develop a gut. It even happens to men who are dedicated runners or those who at least do their daily cardio. A bellyful of studies prove this trend, but all you really have to do is look around at most guys over the age of 35 – the paunchy guts are everywhere.
Many have accepted this. It's often called "dad bod" and has been attributed to beer and bad diets, as well as the "natural" loss of muscle and subsequent puny metabolism as we get older. Science even has a term for it: age-associated waist circumference increase.
Does It Have to Be That Way?
Hell no. Researchers from the Harvard School of Public Health looked into it with a 12-year study on 51,000 male health professionals – from dentists to podiatrists. The study was extensive, but the main thing being investigated was the effects of weight training vs. cardio (defined as moderate to vigorous aerobic activity).
The research team did a good job here. They didn't rely on BMI because they knew that lifters and athletes get screwed by it. They also didn't rely solely on body weight, because losing weight on the scale doesn't mean crap if you're also losing muscle. So they focused mainly on waist measurements, which are difficult to misread.
What they found was a significant inverse dose-response relationship between weight training and waist circumference change. In English, that means that the guys who lifted weights generally didn't grow a big gut. The cardio guys did better than the TV-watchers (the control group), but not nearly as good as the lifters.
Now, the joggers generally didn't gain as much weight as many of the lifters did, but the researchers smartly noted that the weight gained by the lifters was mostly muscle. In short, the lifters looked better naked than the cardio'ers.
The scientists went on to argue that doing both weight training and cardio is probably best... and they're probably right when you factor in other health markers.
So, what can we learn that we didn't already know? Well, if you're trying to avoid central adiposity – a fat gut – lifting weights beats cardio. That still surprises most people, especially the average guy who assumes that cardio would be the most effective form of exercise for battling the bulge.
EPOC (Excess Post-exercise Oxygen Consumption) from weight training explains this in part. EPOC is the phenomenon where, after lifting, you continue to have a higher energy expenditure at rest for up to 48 hours. Cardio may burn more calories while you're doing it compared to most types of weight training, but a lifting workout KEEPS burning calories.
"Another potential explanation is the shift in substrate utilization from carbohydrates (mostly used during unaerobic training such as weight training) to lipid oxidation (mostly used during aerobic training) due to an induced-training adaptation involving increased mitochondrial content in the muscle," researchers added, apparently trying to sound as boring as possible.
So, if you only have time for one form of exercise and you want to avoid dad bod, lift weights. Lots of cardio may slow down the gut growth, but as you age the muscle loss will come back to bite you in the saggy ass.
- Rania A. Mekary, Anders Grøntved, Jean-Pierre Despres, Leandro Pereira De Moura, Morteza Asgarzadeh, Walter C. Willett, Eric B. Rimm, Edward Giovannucci, Frank B. Hu. Weight training, aerobic physical activities, and long-term waist circumference change in men. Obesity, 2014