There’s a lot of conflicting things written about running and sustained cardio exercise. As an avid runner, I would love for the evidence to be firmly on running’s side as beneficial to everyone who wants to take it up. At the same time, I also want people to know exactly what they are getting from running so that they can tailor how they run for their own fitness goals.
For instance, the question “Will running make you fat?” crops up every so often especially when we see people of different shapes and sizes cross the finish line of a marathon. Anecdotally, I’ve experienced both weight gain and weight loss even in a running regimen.
The academic research is clear that aerobic exercise does result in fat loss. In an article on the International Society for Sports Nutrition’s website, Dr. Jose Antonio, Ph.D. lays out several studies from reputable journals that support cardio as a useful tool for shedding body fat.
- A 10-week aerobic exercise program results in a small decrease in energy intake and an associated decrease in a percentage of body fat in obese adolescents. (Thivel, D., et al., Is energy intake altered by a 10-week aerobic exercise intervention in obese adolescents? Physiol Behav, 2014. 135: p. 130-4.)
- Twelve weeks of regular aerobic exercise led to significant reductions in body weight, body fat percentage, and body mass index in the obese. (Lee, S.S., et al., The Effects of 12 Weeks Regular Aerobic Exercise on Brain-derived Neurotrophic Factor and Inflammatory Factors in Juvenile Obesity and Type 2 Diabetes Mellitus. J Phys Ther Sci, 2014.26(8): p. 1199-204.)
- Aerobic exercise training can reduce % body fat and enhance vascular compliance in obese male adolescents. (Song, J.K., et al., Effects of 12 weeks of aerobic exercise on body composition and vascular compliance in obese boys. J Sports Med Phys Fitness, 2012. 52(5): p. 522-9.)
- “Aerobic training is the optimal mode of exercise for reducing fat mass and body mass, while a program including resistance training is needed for increasing lean mass in middle-aged, overweight/obese individuals.” (Willis, L.H., et al., Effects of aerobic and/or resistance training on body mass and fat mass in overweight or obese adults. J Appl Physiol (1985), 2012. 113(12): p. 1831-7.)
- In obese adolescent boys, both aerobic and weight-training exercises for a 3-month period resulted in a loss of total and visceral fat. (Lee, S., et al., Effects of aerobic versus resistance exercise without caloric restriction on abdominal fat, intrahepatic lipid, and insulin sensitivity in obese adolescent boys: a randomized, controlled trial. Diabetes, 2012. 61(11): p. 2787-95.)
However, there are things you need to watch out for that can sabotage your weight-loss efforts. So it’s not running that can make you fat, but weight-loss mistakes you commit while in a running regimen.
Will running make you fat? 3 mistakes you are making
- Eating Mistakes
When I look at my running watch after a half-marathon and find that I’ve burnt over 1,000 calories, there’s a part of me that wants to reward myself by eating a slice of cheesecake. Or I could fall into the trap of thinking that because I’ve burned so many calories, I can eat whatever I want.
Nothing could be further from the truth. It can take someone of my size 30 minutes of running to burn off the 300 calories from a cheeseburger, which I can down in less than five minutes. If I feel like scarfing down the contents of my fridge (which can happen after a monster training session), I can easily over-eat.
There’s also the matter of not eating enough, or not eating the right foods, or at the wrong times. Sports and exercise nutritionist James Collins recommends eating a mix of protein and carbohydrates within 30 minutes after a run to jumpstart the muscle repair process. He also says amount of carbohydrate intake should be higher on days with heavier training load, and lower on lighter days.
Failing to eat properly especially after long and hard runs can cause your body to start cannibalizing its own muscle (a process called “catabolism”) in an effort to get the adequate energy to meet its needs. Losing lean muscle mass in this way contributes to lower resting metabolism, which means you also burn less calories at rest. It becomes a vicious cycle.
- Training Mistakes
The human body is highly adaptable to any sustained challenges you present it. This is how those who were once barely able to run for five minutes eventually are able to complete a marathon with proper training.
However, doing the same kind of training all the time can cause your body to become more efficient at it. That’s great for improving your running economy, but not so good if you want to burn calories. Because running is a weight-bearing exercise, lighter runners also burn less calories on average than heavier runners.
As you become a more efficient runner, you begin to burn less calories for the same distance and effort. If you want to keep burning the same number of calories during your runs, you’ll need to increase the pace or intensity you run at. I don’t mean run every session fast, but you can benefit from some faster-paced sessions, or doing hill repeats.
- Recovery Mistakes
A certain amount of stress to the body’s systems results in beneficial changes that help it adapt. But there is a tipping point where the body is no longer able to handle the stress we put upon it, and its systems can start to break down. This is what happens when we don’t give ourselves enough recovery.
The hormone cortisol is produced by the body to help increase available energy to the muscles. In normal amounts, this is a healthy response and levels of cortisol decrease after exercise. However, when an athlete overtrains, cortisol levels don’t go down. Chronically elevated cortisol levels are linked to increased abdominal fat, problems concentrating, and poor immunity.
It’s important to train smart. This means increasing running mileage and intensity gradually, backing off at signs of fatigue, and getting enough sleep and down-time. A properly-structured training program under the watchful guidance of a coach can give you this.
All things held equal, leaving a sedentary lifestyle and taking up running will result in fat loss. So the answer is No, running will not make you fat.
About the Author
Bochakorn began her education in conventional medicine as a nurse, then shifted to embrace natural healing and integrative medicines. Her training and certifications abroad include: Nutrition and Western Herbal Medicines, Acupuncture and Moxibustion.
During her therapeutic sessions, she may also incorporate other aspects of integrative medicines when required, including: acupuncture, cupping therapy, moxibustion, nutritional, supplements and herbal recommendation.