COLUMBUS, Ohio -- People who lower their fat or carbohydrate intake in an attempt to lose weight might be in for a bigger battle than they expected.
A new study found that people who ate low-fat or low-carbohydrate lunches compensated by eating more fat or carbohydrates at other meals. The result was that participants consumed similar levels of fat and carbohydrates each day, regardless of how healthy their lunch was, said John Allred, leader of the study and professor of nutrition at Ohio State University’s Department of Food Science and Technology.
The findings suggest that the brain’s biochemical signals may play amajor role in people’s food choices, at least where fat, carbohydrates and total calories are concerned, Allred said. He presented the findings April 20 in San Francisco at a meeting of the American Society of Nutritional Scientists.
The study followed 25 male college students for three weeks. Each student was given a Carnation Instant Breakfast shake for lunch every day. Some shakes were made with whole milk, and contained 614 calories. Some were made with skim milk, and contained 516 calories. Some were made with skim milk with added sugar, to increase the calories to 614 calories, without the added fat from whole milk.
Each subject was given a different type of shake for each week of the study, but neither the subject nor the graduate student who administered the study were aware of which type they had.
The students kept food diaries of the food they ate for the rest of the day. The findings were clear: Students who drank the higher-fat drinks for lunch compensated during the rest of the day by increasing their carbohydrate intake and decreasing their fat intake. Students who had the lower-fat, higher-carbohydrate drinks compensated by eating more fat and fewer carbohydrates during the day. Students who had the skim-milk-based drinks without the added carbohydrates increased total calorie consumption throughout the rest of the day.
For example, at eating occasions other than lunch, students who drank shakes made from whole milk (higher fat) consumed 55 percent of their total calories as carbohydrates and 28 percent of total calories as fat. In contrast, students who drank the skim-plus-sugar (higher carbohydrate) shakes consumed only 51 percent of their total calories as carbohydrates during the rest of the day, and 31 percent as fat. Both the differences in carbohydrate and fat intake are statistically significant.
“There seem to be biochemical signals that, unknown to you, regulate calorie, carbohydrate and fat intake,” Allred said. “It says to me that our bodies are much more in control of our food choices than we think they are.”
Allred was surprised at two aspects of the findings. First, he had expected that students drinking the higher-fat shakes would decrease their overall calorie intake at other meals. While that occurred over the first few days of the study, the students adapted by day four and there was no overall difference in calorie intake among the groups. Also, the subjects were asked to keep a log of how hungry they felt just before drinking their lunchtime shake and in the five hours afterwards. The groups’ answers were identical, whether they had higher-fat or lower-calorie shakes at lunchtime.
Allred studied men only because women’s menstrual cycles can affect appetite and eating behaviors. Also, he stresses that all the men in the study were “unrestrained eaters,” meaning that they usually ate what they wanted to eat and didn’t analyze their food choices in order to lose or gain weight or for some other reason. This is important because the brain can override other biochemical signals, Allred said.
In the next phase of the study, Allred will actually look for the biochemical signals that control eating. The students gave blood samples once a week during the study, which Allred will analyze to try to find which biochemical signals are present under each condition.
The study was sponsored by a grant from the National Dairy Council.