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Does Increasing Fruit and Vegetable Intake Affect Weight Loss?

Does Increasing Fruit and Vegetable Intake Affect Weight Loss?

Health and Wellness

August 27, 2014

Current studies do not support the claim that increasing the intake of fruits and vegetables contributes to weight loss, according to a recent study from the University of Alabama at Birmingham and published in The American Journal of Clinical Nutrition. The study found that, while a common recommendation for weight loss is to increase the consumption of fruits and vegetables, there is no scientific basis to support this claim.

Dr. Kathryn A. Kaiser, Ph.D., study co-author, says that they were interested in examining this health claim because they did not think it was intuitive that by eating “more” of foods that contain energy (i.e., calories) one would lose weight. Yet, this message is found in many health campaigns such as “More Matters” and in the 2010 Dietary Guidelines for Americans, so they decided to find any experiments available that actually tested this dietary approach.

Kaiser and team searched multiple databases for human randomized controlled trials that evaluated the effect of increased fruit and vegetable intake on body weight, focusing on single approach interventions in order to find the independent effect of the one intervention. Two studies met all the criteria; 5 other studies met all criteria but one. Criteria included that the stated goal of the intervention was weight or fat loss or the prevention of weight or fat gain and that the food intake prescribed was a variety of fruits and veggies that were minimally processed. 

“We found that increased fruit and vegetable consumption resulted in no weight change (up or down) on average. Our aim was to hopefully refine the public health messages so that ‘replacement’ is used instead of ‘more’ with regard to consciously eating more foods of lower energy density while reducing intake of foods higher in energy density so that there are fewer net calories being consumed,” says Kaiser.

Interestingly, Kaiser says that increasing a higher proportion of vegetables over fruits might be more beneficial toward helping with weight loss. Since some fruits are higher in carbohydrates than many vegetables, this can translate into more energy being consumed if a person’s diet is very high in high carbohydrate fruits. However, most fruits do not approach the energy density of many packaged, restaurant, or even some home prepared foods, so they can still be a good substitute to lower ones’ net energy intake.

Fruit and vegetable intake has many benefits, such as contributing micronutrients, fiber and phytochemicals that are associated with reductions of risk for things like heart disease, certain cancers and diabetes. They may even be able to help satiate hunger. In fact, it appears that people may experience different effects on hunger perceptions from higher fiber diets, at least in the short term. “Since the management of hunger seems very important to maintaining a lower calorie diet, identifying foods that are lower in calories but reduce or delay hunger feelings may be useful. These may not be the same for everybody, but each person can experiment for themselves,” says Kaiser.

Meanwhile, as to why there is so much messaging about increasing fruits and vegetables for weight loss purposes, Kaiser says this may be due to a “halo effect” that has developed in our food culture, and she hopes their message can help to put weight loss diets in a more accurate perspective. 

“Some scientists put ‘spin’ in their writing about the results of their studies, so it is more difficult for the lay public to interpret study reports in the proper context. It does not help that popular or medical media outlets use magical language when describing certain foods (often about fruits and vegetables) as having ‘super’ or ‘miracle’ effects on body weight,” says Kaiser.

Researchers cannot predict how others will change their communication of fruit and vegetable intake in the future, but Kaiser hopes that the messages are refined so that anyone who receives the messages can know how to eat a better diet for their personal health goals, and that the recommendations are based on scientific data. 

“We still have much to do in the human nutrition research arena to get to that point. Retailers and health professionals may have very different aims, but we hope that any messages given are based on facts. We hope our study results add to the basis for these facts,” adds Kaiser.