A publication in PeerJ documented compelling evidence that exercise might not be the key to controlling body weight.1 This study found that over three years, total weight gain was greater among participants who met the physical activity guidelines of two and a half hours a week compared to those who did not.

This leads us to the question: Does exercise lead to weight gain and possibly obesity?

As we dig into this question, I want to be clear that the reason we prescribe exercise is not to lose weight. We prescribe exercise because it prevents disease and is part of a healthy lifestyle.

This publication is one we must all understand because it helps illustrate the daily challenges every patient goes through with exercise adherence, food choices, weight loss and progress.

When prescribing exercise to your patients, remember this: You are not attempting to get your patients to start exercising; you are attempting to get your patients to change a behavior pattern—and that can be extremely difficult.


Exercise Does Not Beat a Sedentary Lifestyle

Wake up, drive to work, sit at a desk for eight hours, drive home, eat dinner, watch television and go to sleep. Repeat. That’s a day in the life of most Americans, and, as you can see, a lot of time is spent being sedentary. Even if we squeeze in 30 minutes of moderate exercise, it still doesn’t change the negative effects of sitting for long stretches.

This lifestyle pattern led researchers to coin the phrase, “sitting is the new smoking,” because they documented that having a sedentary lifestyle is as predictive of cardiovascular disease as smoking.2


We All Cheat (a Little) on Diet and Exercise

As a former dietician and exercise physiologist, lifestyle medicine is my life. I pride myself on the fact that I exercise daily and eat a whole-food, plant-based diet. But last week after lunch, we were celebrating a colleague’s birthday with cookies. Naturally, I picked up a cookie and ate it. My internal justification was, “It’s okay to eat this cookie. I got in a great workout this morning.”

How familiar does that sound? Sure, in the long term, it’s only one cookie, and I am usually diligent with my lifestyle choices. But for most patients who haven’t been so diligent, that cookie mindset applied repeatedly is a big deal, and it will affect them long term.

In fact, researchers found that given the ability to choose the amount of food you eat, people ate more after an exercise session—and even more still if the exercise session was intense—than people who did not exercise.3


Exercise Advice to Keep Your Patients On Track

One pearl I will always remember from my time as a clinician was just how much patients exaggerated their diet and exercise programs. During consults, I’d frequently hear something like, “Yes, I exercise every day, and I eat a huge salad with salmon for lunch,” from just about every patient. But when I’d examine their food and exercise logs, they would tell a significantly different (i.e., worse) story.

The truth is that self-perception of compliance to a lifestyle-based program often does not line up with reality. To illustrate that, a group of researchers looked at self-reported frequency of exercise. They found that males and females exaggerate their exercise frequency by 44% and 138%, respectively.4

So, what do we do about this?

It’s important to remember one of the greatest challenges for patients is to change behavior patterns surrounding the simple choices they make each day. Knowing this, we must stress the following tips:


1. Don't be an exercising couch potato!

Challenge patients to set a cell phone alarm to go off every 45 minutes to remind them to get up and take a walk. Even if that walk is to the water cooler and back, it still counts!


2. Don’t fill your Ferrari with orange juice.

The body is an engine and needs to be fed properly. Remind patients not to reward themselves for exercising by cheating on a healthy diet.


3. Journal every day.

For at least the first 30 days of a program, encourage patients to keep a daily diet and exercise log. This will give them an idea of the challenges they face each day and help them find ways to improve compliance.


So... Does Exercise Lead to Weight Gain?

To answer our original question: No, exercise does not lead to weight gain and obesity, but exercise is also not the only determining factor in weight loss. Continue to remind your patients that the goal of exercise is not to lose weight. The goal of exercise is to be healthy and prevent disease!




Jonathan Cannizzo, MSc

Jonathan Cannizzo, MSc has worked as an exercise physiologist and dietician, helping prescribe and program lifestyle medicine at both Advocate Health Care and Cenegenics Chicago. He earned his Masters of Science in Cell Biology and Biochemistry with a focus on chronic disease progression from Northeastern Illinois University and his Bachelor of Science in Exercise Science from the University of Central Oklahoma. As a graduate assistant at Northeastern, Jonathan was the primary author of chapter 6, Cancer, in the text Diet, Exercise and Chronic Disease: The Biological Basis Behind Prevention.





1. Dugas LR, Kliethermes S, Plange-Rhule J, et al. Accelerometer-measured physical activity is not associated with two-year weight change in African-origin adults from five diverse populations. PeerJ. 2017;5:e2902. Published 2017 Jan 19.
2. Biswas A, Oh PI, Faulkner GE, et al. Sedentary time and its association with risk for disease incidence, mortality, and hospitalization in adults: a systematic review and meta-analysis [published correction appears in Ann Intern Med. 2015 Sep 1;163(5):400]. Ann Intern Med. 2015;162(2):123-132.
3. Pomerleau M, Imbeault P, Parker T, Doucet E. Effects of exercise intensity on food intake and appetite in women. Am J Clin Nutr. 2004;80(5):1230-1236.
4. Prince SA, Adamo KB, Hamel ME, Hardt J, Connor Gorber S, Tremblay M. A comparison of direct versus self-report measures for assessing physical activity in adults: a systematic review. Int J Behav Nutr Phys Act. 2008;5:56. Published 2008 Nov 6.