Fewer people have time to cook these days, which means more people are eating processed and packaged foods. The rise in obesity rates in America have closely paralleled the rise in consumption of processed foods. This isn’t surprising since packaged foods are usually higher in calories and contain more unhealthy forms of fat and sugar – but that may not be the only reason. A study shows you may burn fewer calories after you eat a processed meal than after you eat a similar meal consisting of whole foods.
Processed Foods and Their Effect on Fat-Burning
Researchers at Pomona College conducted an interesting experiment. They gave 17 volunteers cheese sandwiches to eat. On one day, they ate a cheddar cheese sandwich on whole grain bread. On the second day, they ate a sandwich made with processed cheese on white bread. Both sandwiches had similar calorie contents and an equal amount of protein, carbohydrates, and fat.
After eating the sandwiches, the researchers measured the metabolic rate of the volunteers every 6 hours. The results? The volunteers burned 137 calories after eating the sandwich made with real cheddar cheese and only 73 calories after munching on the processed cheese sandwich.
The Thermic Effect of Food
After eating a meal, your body expends energy to break down and process what you’ve eaten. The additional calories you burn after eating a meal is called the thermic effect of food, and it varies with the composition of the food you’ve eaten. For example, eating a food high in protein has more of a thermic effect than chowing down on one high in fat. That’s one reason why high-protein diets help with weight loss. The thermic effect of food isn’t insignificant. It accounts for up to 10% of your daily energy expenditure.
Based on this study, a processed cheese sandwich had less of a thermic effect than a sandwich made with real cheddar cheese on whole grain bread, despite the similar calorie and nutrient composition. In fact, the thermic effect of the processed cheese sandwich was 50% lower. You would burn an additional 64 calories if you snacked on the real cheese sandwich over the processed one. If you replaced processed foods with whole foods, you could end up burning significantly more calories due to the additional thermic effect of eating whole foods.
Why do processed foods have less of a thermic effect? In this study, the cheese sandwich made with whole grain bread was higher in fiber because of the grains in the bread. Fiber helps to reduce the rise in insulin levels that occurs after a meal. Research has linked higher levels of insulin after a meal with decreased thermogenesis and fat burning. In addition, insulin is a hormone linked with fat storage, so avoiding processed foods that spike insulin levels are a good strategy for weight control.
The Bottom Line?
Now there’s another reason to eliminate processed foods from your diet. Plus, processed and packaged foods have less nutritional value than comparable whole foods. Add more fresh fruits and vegetables to your diet and enjoy a variety of lean protein sources like fish, turkey, tofu, and lentils that have a strong thermic effect – then enjoy the afterburn.
Food and Nutrition Research. 2010. 54: 5144.
J Clin Invest. 1992 March; 89(3): 824-833.