Exercise ‘makes’ you eat healthier
by Geraldine Hinter
Undertaking regular moderate exercise can trigger healthier eating choices in overweight and obese people, a University of South Australia study shows.
PhD researcher and lecturer in nutrition at the School of Health Sciences, Kathryn Jackson conducted a 16-week exercise program to determine whether regular moderate intensity exercise influenced individuals to make voluntary dietary changes, without being given any dietary counselling, advice or guidelines for healthy eating.
Participants in the study included sedentary men and women with an average age of about 40 years in full-time or part-time work, unemployed, or at home with young children. All were either overweight with a body mass index (BMI) greater than 26, or obese (BMI greater than 30), with most in the obese category.
"Study participants were asked not to go on a diet and to eat what they felt like eating, with no restraints; but they were required to exercise for 45 minutes to an hour three times a week in a controlled and supervised environment. Exercises included aerobic, weights and resistance training, and a gym circuit," Jackson said.
"We selected exercise programs of moderate intensity that participants could do and feel benefits from, as well as increase their fitness levels. And we looked at their food intake at the start and again at the end of the study to see if any changes had taken place.
"Not only did participants adopt healthier food choices, but at the end of the study, all of them, both men and women, had lost weight and in particular, had lost body fat. They also increased their lean muscle mass, which can be expected when adhering to regular exercise," Jackson said.
"The weight loss was mild, with men losing about 1.5kg and women nearly twice that amount, but they carried more body fat at the beginning of the study. Importantly, both the men and women in the study reduced their fat intake by about nine grams (equivalent to about two teaspoons of margarine) on average per day."
And while that might not seem a lot, Jackson said it was statistically significant and it showed that a small drop in fat per day could make quite a difference, especially when exercise was added.
"Even more astonishing was that they dropped their total energy intake, not just the fat component, but also their carbohydrate and protein intake," Jackson said.
"We also looked at food weight and beverage weight, based on their records, and found that no one had increased their portion sizes or the amount of food they ate. They had adopted the Australian dietary guidelines without even trying. It was quite remarkable to see this happening in a previously inactive group of people," she said.
Jackson said that providing the exercise environment helped to get them moving and keep them moving. Part of their dietary behaviour change could be attributed to having someone monitor and control their program.
"The take home message is that you don’t have to follow a diet and start exercising but if you start exercising, the results of our study suggest that undertaking regular exercise of moderate intensity influences people to make healthier food choices," Jackson said.
"The whole mindset in people changes because they are making a lifestyle change by exercising, and studies in the Netherlands and the United Kingdom show alterations in taste preferences once people are exercising – a factor that dictates subconsciously their food choices – but I think it’s also the wellbeing attitude that is adopted because of the exercise."