It’s the fast food

Eating studies have suggested a number of factors that might be affecting the amount people eat when they eat fast food. First and most obviously, the portion sizes have increased. Second, people tend to eat fast food meals more quickly, which can override the body's natural signals of fullness. Further, fast food is what we call "energy dense": it's high in calories for its physical size.

Would breaking up a fast food meal into multiple smaller portions or causing them to simply eat more slowly help to reduce the amount a person ate? Scientists at Children's Hospital in Boston, Massachusetts designed a study to find out (Pediatrics 2007;119(5):869-875). They recruited 18 overweight adolescents between the ages of 13 and 18 who admitted to eating fast food at least once per week. (The children's parents all gave permission to participate.)

On three separate occasions the children were each given a fast food meal consisting of chicken nuggets, French fries, and sugared soda. The size of the meal was designed to be so large that the child would stop eating before they finished all of the available food. (This way the scientists knew that a too-small portion size was not causing the child to stop eating.)

On each of the three occasions the meal was presented a little differently, with each variation selected randomly for each child. On one occasion the meal was presented all at once in one large portion, just as it might in a fast food restaurant. On another occasion the meal was divided into four equal portions, but was still was placed before the child all at the same time. Then on yet another occasion the meal was divided into four portions and a single portion was given to the child every fifteen minutes until the child received all four portions.

The scientists had thought that the meal that forced the child to eat more slowly - the one with the fifteen minute delay between portions - would result in the child eating the least. Wrong! They were surprised to see that no matter how the meal was presented, the children still ate about twice the calories they needed. They concluded that the trouble is not that people eat fast food too quickly, or that the extra large portions were leading people to overeat, but rather the trouble is with the fast food itself.

What this means for you

One of the first things we tell our patients when they say they want to lose weight is to cut fast food out of their diet. It has nothing to recommend it - it's not good food and it's full of fat, salt and added sugar with very little fiber. Keep your children out of fast food joints if you possibly can, but at the very least don't super-size the meal!

First posted: May 8, 2007