You know you don’t have the healthiest diet. Most of your meals come from a box or a can. Vegetables are the exception, not the rule. You’re frustrated and you know you need to eat more healthily, but you need someone or something to light a fire under your sedentary behind. According to new research, you might be more inclined to improve your diet if you get moving, first.
Molly Bray, study co-author and chair of the department of nutritional sciences at the University of Texas at Austin, said:
“It’s hard to start a diet. Most people feel deprived from the get-go. Instead of taking something away, you can add physical activity to your life, and the consequent changes may be significant changes in the way you eat.”
For the study, Bray and her colleagues recruited more than 2,500 college students who said they didn’t eat healthily and exercised for less than 30 minutes a week. The researchers put the students on a 15-week aerobic exercise plan involving guided cardio lasting 30-60 minutes, 3 times a week. Each participant was asked to fill out a diet questionnaire at the beginning and end of the study. They were also instructed not to alter their eating habits.
However, many of the students did change their diet. About 2,000 of the recruits stuck with the exercise plan, and they turned out to be more likely to start eating healthier without being instructed to, the researchers found. Many of the exercisers started adding more healthy foods to their diet, including fruit, vegetables, lean meats, fish, and nuts.
Moreover, their diets started to include fewer fried foods, soda, and junk food. The more a student exercised, and the more vigorously they did so, the more their diet tended to improve, the study showed.
The longer an individual worked out, the less likely they were to consume fried foods, snack foods, and red meat. What’s more, high-intensity exercise was associated with an increase in preference for healthy foods. According to Bray, this means that “compliance with the exercise program was associated with a move toward eating healthier overall.”
Exercise Changes the Brain
The study didn’t tease out the reasons why exercise leads to healthier eating patterns. That is something researchers will investigate in future studies. But Bray said the reasons are both psychological and biological.
“There’s a lot of research that positive results fuel adherence and persistence and other changes physiologically. Some people may be saying, ‘Wow, look, my shorts feel looser. I’m going to work on my eating behavior.'”
It’s such a simple mental trick, but it makes a lot of sense. When you see yourself making progress in one area of your life (physical activity), the last thing you want to do is tank your progress by neglecting another area of your life (diet). Yet, Bray said there is more to it than that.
“I really do think exercise is altering neural processing in your brain. The stimulation of your brain that occurs with high-intensity exercise is what changes a lot of things about your body.”
Previous studies show a relationship between the intensity of exercise and the amount of appetite-regulating hormones in the body. Additionally, researchers have shown that moderate exercise can change dopamine levels in the brain in such a way that a person craves fewer fatty foods. 
However, Bray cautioned that eating more healthily isn’t likely to convince you to start exercising, as she doesn’t believe that food choices alter the brain the same way that exercise may. Plus, most people have an easier time of starting an exercise routine than they do starting a restrictive diet. 
“Add something to your life – what a good health message. This is a gift you’re giving yourself, and other really significant health changes can occur along the way.”
“Many people in the study didn’t know they had this active, healthy person inside them. Some of them thought their size was inevitable. For many of these young people, they are choosing what to eat and when to exercise for the first time in their lives.”