Why lifting weights beats cardio for fat loss [New research]

Chaprters:

00:00 Intro

00:20 MH Physique App

00:41 New Aerobic vs Strength training study

01:59 Recent meta-analysis

02:44 How does the fat loss work?

05:02 Constrained energy expenditure

05:58 Conclusion

06:58 Outro

Transcript:

Mainstream fitness wisdom tells us that cardio is best to get lean and toned, whereas lifting weights is best to get big and bulky. In reality, the only two things under your control that determine how your physique looks outside of genetic factors are your level of muscle mass and your body fat percentage. A new paper found that lifting weights is actually best for both of these.

Before going into the study details, I’d like to mention that my Physique app is now out of the testing phase and available for download. You can try a two week free trial and it will give you a fully optimized training and nutrition program. And as you start using the app, the app will coach you and keep your program updated based on your progression to reach your goals as fast as possible. You can get a two week free trial with the link in the description.

Onto the new study. The researchers had a group of 304 men and women that were on a fat loss diet with approximately 500 calorie energy deficit and a protein intake of 1.5g/kg per day choose to do either aerobic exercise for about 200 minutes per week, strength training 2 to 3 times per week, or no exercise at all. The self-selection of exercise in this study was done to improve exercise adherence, but it does have the downside of potentially having selection bias because it was not randomized. The subjects dieted until they had reached a healthy body fat level, which took on average five months. So this is a pretty good sample size with a pretty good duration. After this period of five or so months, the strength training group actually had the most fat loss in absolute terms on all measures. However, this was only statistically significant for the women, specifically for abdominal circumference. For most of the other measures, statistically, fat loss was similar between two groups.

Obviously, strength training was the most effective for muscle growth as measured by increases in fat free mass. The aerobic exercise group in fact lost lean mass, while the strength training group was the only group that built lean mass. The researchers therefore concluded that strength training is essential and critical for fat loss programs. I agree. Since strength training is equally effective as cardio to lower body fat percentage, and it’s more effective to increase muscle growth and strength development, it is the better package deal.

The finding that resistance and aerobic training are equally effective to lower body fat percentage is also supported by another recent meta-analysis of 31 studies. In this analysis aerobic exercise on average did result in greater absolute increases in fat loss, but because strength training was more effective to increase fat free mass, body fat percentage losses were similar. Importantly, in studies that were equated for time or energy expenditure or total work output, there was no difference even in absolute fat loss between strength training and aerobic exercise.

Since for most individuals all forms of exercise compete for a limited amount of time that we have, the results that you get per minute of training are most important. And in this sense strength training offers you more muscle growth and equal decreases in body fat percentage. It might seem also that aerobic exercise is no more effective than strength training to lower body fat percentage, but it actually makes perfect sense when you understand how fat loss works. See, most people think that cardio makes them lean, or cardio directly burns body fat. It does not.

While cardio does oxidize fatty acids, in the end your total body fat loss is dictated by energy balance over time. This means that your total energy expenditure is really the key variable. And this is also what the meta analysis found that when you equate for energy expenditure all forms of exercise are essentially equally effective in the short term. Strength training, however, has the added advantage of building muscle mass, not just preserving it, but actually increasing it, in many studies, especially in lesser trained individuals or individuals with higher body fat levels.

Preserving or building muscle mass is not just important for people that want to look more muscular. It is also directly relevant for fat loss because when you have an energy deficit your body has to make up these energy deficit because you are expending more energy than you are consuming, and it’s burning some of your own tissue to make up for the difference. It only burns this once, so any muscle that you lose is fat that you’re not losing. The more muscle you lose on a diet, the less fat you lose.

Moreover, muscle growth is an energetically costly process. It increases energy expenditure. Not just short term, but also long term. This means that over the longer term we would expect the advantage of strength training to increase while aerobic exercise becomes less effective per unit of time because the investment per unit of time is just for that one workout and burning some energy now, whereas what strength training does is it burns energy now, but it also builds muscle mass, which increases energy expenditure over the long term.

Now the increase in energy expenditure from having, say, one more kilo of muscle mass is fairly insignificant. A few calories in most estimates. However, the increase in total daily energy expenditure is more significant because it’s not just that you have one more kilo of muscle mass that your body has to maintain, it’s also that you have to lug that mass around during the whole day. If we look at studies that measure a resting energy expenditure, we see that even a few months of strength training can already make a significant difference in your resting energy expenditure on the order of a couple %. And then if we look at longer term comparisons between, say, bodybuilders and matched control subjects, we see that the difference can be some 15 or so % in resting energy expenditure. Again, for total daily energy expenditure, the difference becomes even more significant.

Another, more technical reason that strength training performs very well vs. cardio in terms of fat loss is that cardio and physical activity in general of a lower intensity is subject to constrained energy expenditure. Energy expenditure rises the more active you are. But there is a limit, or at least there is some constraint. Rather than a linear increase in energy expenditure with higher levels of physical activity, we see that there are diminishing returns. This is called constrained energy expenditure.

Now it seems that strength training does not suffer from constrained energy expenditure. It seems to be that it’s too high intensity and the body cannot have a sufficient compensatory response to decrease energy expenditure from the energy expenditure that is required for strength training. In contrast, walking more or doing lower intensity cardio is in many studies associated with constrained energy expenditure and energy compensation, with some analyzes saying that the average is some 28% lower energy expenditure than you would expect, based on the increase in physical activity.

Now, if we zoom out even more and look at even longer periods of time, then generally the increase in energy expenditure from training is just not that significant versus your diet. Whether you eat less or you burn more calories with exercise does not matter for fat loss. In the end, it just comes down to energy balance. So for most individuals, what I teach to my students and my clients is that you really want to focus your exercise on health, performance, and muscle growth.

The sayings that “you can’t out train a bad diet” and “abs are made in the kitchen” are very true. For physique purposes that means that most individuals are best off doing strength training or resistance training in general for the first couple of hours of exercise per week. Only when you get to the point that further strength training becomes difficult in terms of overreaching and recovery, then it becomes a consideration to add some more cardio to increase energy expenditure further. Even then, though, I really recommend focusing on the long run, thinking about sustainable lifestyle change and in particular changes in your food choices, because for most individuals that is the most important to get and stay lean.

I hope this knowledge helps you with your fat loss. If you like this type of evidence-based content, I’d be honored if you like and subscribe. And if you’re interested in my app, check out your two week free trial in the link below.