One of the most common questions I’m asked as a Personal Trainer is, “what’s better for losing weight, resistance training or cardio”? My response to this question is always the same… neither will make a difference if you’re consistently eating too much food. The hard truth is, if you want to slim down you need to focus on your diet. Specifically, you need to consistently eat in a calorie deficit, aka eat less food than you burn.
Now that we have established the importance of diet we can talk about cardio vs. resistance training. Between the two, resistance training is the clear winner! Resistance training can aid in the weight loss process, but the real reason it is superior to cardio is because it will help to preserve your muscles. When you are in a calorie deficit you lose fat, but you also lose a lot of muscle mass. We absolutely do not want this. Your muscles are what give your body shape. In order to preserve our muscles, we need to implement resistance training. Cardio can be a useful tool during the weight loss process, but it just is not going to save your muscles.
The importance of resistance training has been demonstrated in the scientific literature as well! In one study, twenty participants (17 women and 3 men) were put into a super aggressive calorie deficit consisting of only 800 calories a day (side note: I would never recommend anyone eat only 800 calories a day!!!). The participants were divided into two groups; one maintained a calorie deficit while performing weekly cardio while the other maintained a calorie deficit while engaging in weekly resistance training. After 12 weeks, both groups lost a significant amount of bodyweight. However, the cardio plus diet group lost a ton of muscle along with fat, while the resistance training plus diet group maintained all of their muscle and only lost fat![1]
Another interesting study from 2008 found similar results. In this study, 94 female participants were each put on an 800-calorie per day diet and split into three groups. The first group just dieted without engaging in any type of exercise, the second group combined diet and cardio and the third group combined diet with resistance training. All three groups lost weight but only the resistance training group maintained their muscle mass and their strength.[2]
Now that we have established the importance of resistance training, let’s talk about cardio and when/how it should be incorporated into your weight loss plan. Cardio can be a great addition to your diet because it can allow you to eat a bit more food, which may help you stick with your diet longer. For example, say in order to lose weight you need to be in a 500 calorie a day deficit (which equates to about 1lb of weight lost a week). You have the option of reducing the calories you eat by 500 or you could only reduce them by 300 and burn the other 200 doing some sort of cardio. The other reason you can include cardio is simply because you like it – yes, people like that actually exist! If cardio is something that makes you feel good then totally go for it.
[1] https://pubmed.ncbi.nlm.nih.gov/18356845/
[2] https://pubmed.ncbi.nlm.nih.gov/10204826/#affiliation-1