The prevalence of obesity in the United States has reached alarming proportions with 33% of adults over the age of 20 being overweight. Obesity is more than twice as prevalent, however, in the Pima Indians of Arizona. Although there have been a number of advances in our understanding of the genetics of obesity, the environmental influences on the genetic expression of obesity requires further investigation.

In an effort to understand some of the influences on the high prevalence of obesity in the Pima Indians, the present study was designed to investigate eating behaviors and food preferences, most especially the preference for high fat foods, in sib-pairs of Pima Indians who have been previously genotyped in our genomic scan for loci linked to diabetes/obesity. Most specifically, we will utilize several questionnaires and methods of assessing eating behavior and the preference for high fat foods to create a food intake phenotype. As food intake influences appetite-regulating hormones and vice versa, we also plan to assess the effect of short-term overfeeding on ad libitum intake and the appetite-stimulating hormone, ghrelin. Also, as the body's metabolism of carbohydrates may influence food intake, we propose to look at the effects of isocaloric high fat and high carbohydrate diets on short-term ad libitum intake. We will study Pima Indians and Caucasians so that comparisons can be made between these two groups. We will make these evaluations by assessing eating behavior, food preferences including usual fat intake and preferences for high fat foods, body image perceptions, and energy expenditure. It is hoped that the data gathered from this study will elucidate some of the risk factors for the development of obesity among the Pima Indians.

• INCLUSION CRITERIA:

Healthy, as determined by medical history, physical examination, and laboratory tests.

Diabetic, if recently diagnosed (within the last 6 months) and not taking any diabetes medications (original study only).

EXCLUSION CRITERIA:

Hypo or hyper thyroid

Blood pressure greater than 160/95

Cardiovascular disease

Gallbladder disease

Alcohol and/or current use of drugs (more than 2 drinks per day and regular use of drugs such as amphetamines, cocaine, heroin, or marijuana)

Psychiatric conditions or behavior that would be incompatible with safe and successful participation in this study, including claustrophobia and eating disorders such as anorexia or bulimia nervosa

Use of medications affecting metabolism and appetite

Pregnancy

Smoking

Diabetes diagnosis (overfeeding study arm and macronutrient study arm).