What's Better for Fat Loss?..... Dieting or Cardio?

Ask any fitness professional what’s best for fat loss—dieting or cardio, and you’ll get a nearly universal answer of ‘dieting’.

But is that really true?

Most of the published studies that have compared dieting vs. cardio for fat loss have reported that dieting is superior for fat loss. But most of the research in this area is flawed!

Both cardio and food restriction (caloric deficits) are effective for creating a negative energy balance and inducing fat loss. Unfortunately, several problems emerge from the scientific literature when making this important comparison.

The main problem that surfaces in this area is the fact that when cardio and diet are compared for their effects on decreasing body fat, the negative energy balance induced by the diets and exercise programs are not equated. In many instances, there is a much greater caloric deficit induced by the diet as compared to the energy deficit created by exercise. Unfortunately, this introduces an unfair playing field for the exercise condition, leading many studies to conclude that dieting is superior to exercise for fat loss. But they fail at addressing the differences in the energy/caloric deficits created by the diet and the exercise program.

So, who were the participants in the study referenced?

Overweight and obese males. To qualify for the study, the subjects had to have a BMI greater than 27, a waist circumference greater than 100 cm (39 inches), and have been weight stable for the previous 6 months before participating in the study.

Basically, to get into this study you had to be male and overweight/obese. The subjects were sedentary and were not taking any medications that would have impacted body composition or metabolic rate.

They were divided in 4 groups but we will only reference 2 of them. The control group and group instructed to change nothing don’t matter to us at the moment.

We will address the Cardio Only Group and the Diet Only Group for the purposes of this article.

The participants in the Diet Only Group were instructed to reduce caloric intake by 700 calories every day. They were also instructed to perform no form of exercise as to keep any fat/weight loss coming from caloric restriction only.

The participants in the Cadio Only Group were instructed to perform daily exercises, brisk walking or jogging on a treadmill. The length off each exercise session was determined by how long it took the participant to burn 700kcal. This averages out to about 60 min on the treadmill at approximately 80% max heart rate.

So, what were the results?

At the end of the 12 week weight loss period, the overall total weight loss was nearly identical. Both groups lost 8% of their total body weight (16 pounds [7.4 kgs] for the Diet Only group and 17 pounds [7.6 kgs] for the Cardio Only Group).

The big differences came when we start to look at fat loss vs. muscle loss. The Cardio Only Group lost significantly more body fat (-4.3%) as compared to the Diet Only Group (-3.4%).

Further, the Cardio Only Group lost less muscle mass (-2.2 pounds [1 kg]) as the Cardio Only Group (-4.8 pounds [2.2 kgs]).

When looking at the composition of overall weight loss, the Diet Only Group lost just under 70% of their body weight from body fat and ~30% from muscle mass and the Cardio Only group lost just over 85% of their body weight from body fat and ~15% from muscle mass stores.

Another huge part of this study was the fact that the researchers assessed resting energy expenditure (RMR or resting metobolic rate). Which accounts for roughly 60-75% of overall daily energy expenditure. So naturally the higher one is able to keep their REE the more food they can have without gaining body fat.

During the study, the Cardio Only Group was able to maintain their REE much better than the Diet Only Group. Specifically, the decrease in REE in the Diet Only Group was 40% greater (-211 kcals) as compared to the Cardio Only Group (-126 kcals)!

And being that muscle percentage was higher in the Cardio Only Group, this is not surprising as simply having more muscle allows you to burn more calories throughout the day. Allowing you to maintain a higher RMR!

This will also likely aid them in the ability to not regain the weight in the weeks following the study.

So, is creating fat loss through diet or exercise better?

Well, once again this is going to come down to the individual. We have proven that both methods are viable options for creating fat loss. So it comes down to the individual and their life style, responsibilities, and obligations.

Say you have a busy parent, who must manage getting 3 children to and from school, make meals, go to work, run errands, and it’s hard enough to spend 45 minutes to an hour in the gym 3 days per week as it is. Then you are going to ask them to spend another potential hour on the treadmill. Probably not the best route to take.

In this instance creating a caloric deficit via diet is probably going to be the more sustainable and achievable path.

So my opinion is that like anything else in the fitness and nutrition world, the best route to take is the route that is more sustainable and appealing to the client. Whether it be diet or exercise, whatever method you can sustain consistently is the method that you should choose.

Of course a combination of diet and exercise (weight training and cardio) is going to be your best and most effective means of fat loss while maintaining as much lean muscle and RMR as possible.