The purpose of this study is to find out how the amount of fat or sugar in a person's diet,
or the number of meals eaten each day, affect the amount of fat that people's bodies make,
the types of fats in the bloodstream, and how much fat is stored in the liver. The study is
funded by the National Institutes of Health.
The study consists of two 10-day feeding periods that are separated by approximately two
weeks. During each feeding period all food and beverages to be consumed will be provided by
In Study 1, participants will be randomly assigned to receive one of two diets. Both diets
are designed to maintain weight at a constant level. The diets are balanced nutritionally and
have the same amount of protein. One diet has higher amounts of sugar, while the other has
higher amounts of fat. For one 10-day period, the diet will be fed as two large meals
('meal-feeding'). For the other 10-day period, the identical diet will be fed as 8 small
meals ('nibbling'). Half of the participants will meal-feed first, while the other half will
'nibble' first. The order of nibbling or meal feeding will be determined randomly.
In Study 2, the number of meals eaten per day will remain fixed at three (no nibbling or meal
feeding). Participants will receive both the diet higher in sugar and the diet higher in fat.
However, they will be randomly assigned to start one followed by the other for each 10-day
At the end of each 10-day feeding period, participants will spend two nights in a research
ward (Clinical Research Center) to undergo testing.
- overweight or obese men and women
- ages 20-65 years
- pregnancy or lactation within the past six months
- type 1 or 2 diabetes mellitus]
- AST and ALT above upper limit of normal (ULN)
- fasting triglyceride or total cholesterol levels >ULN
- Hgb below the lower of limit of normal
- positive HIV antibody test or hepatitis serologies
- use of any antidiabetic medications or lipid-lowering drugs
- history of surgery for obesity
- change in body weight >5% within preceding 6 months (self report)
- claustrophobia, presence of metal implants
- weight over 350 lbs