Effect of Isocaloric Ultra Processed Versus Unprocessed Diets on Insulin Sensitivity

Overview

Background: Increases in obesity, diabetes, and some metabolic disorders may be linked to how much processed foods people eat. Researchers want to learn more about how processed foods affect metabolic health. Objective: To learn about how a processed versus unprocessed diet affects the body. Eligibility: Men ages 18-50 with stable weight and risk factors for diabetes Design: Participants will be screened over 3 visits. Screening includes: * Medical history and physical exam * Heart and blood tests * Psychiatric questions * Questions about eating, sleeping, and economic status * Riding a stationary bike * Trying a sample meal Between screenings, participants will eat prepared meals. They will wear an accelerometer to measure physical activity. They will write down what foods they eat and monitor their weight. Participants will have two 4-week stays in the clinic. They will: * Eat a special diet * Have activity and weight monitored * Drink water and collect urine samples to measure how many calories they are burning * Have resting energy expenditure measured with a clear hood over the head * Have a scan to measure body fat and bone density using low-dose x-rays * Have a scan on a table that slides into a metal cylinder in a strong magnetic field. They will get earplugs for the loud noises. * Have an ultrasound test to measure blood vessels * Have insulin and glucose infused into an arm vein. Blood will be taken over 10 hours through a plastic tube in the wrist. This will happen 4 times. * Spend multiple 24-hour periods in a room that measures oxygen used and carbon dioxide produced. * Give blood, urine and stool samples * Answer questionnaires and do computer tasks

Nutrition science is beginning to place less emphasis on the nutrient composition of the diet and more emphasis on its comprising foods. A particular public health concern involves the consumption of foods that result from extensive industrial processing. Ultra-processed foods have become increasingly common and now contribute the majority of calories consumed in America. The rise in the prevalence of obesity, type 2 diabetes, and metabolic syndrome over the past several decades is believed to have been caused, in part, by the parallel increase in production, advertising, and consumption of ultra-processed foods. However, the metabolic effects of industrial processing per se, independent of diet calories or macronutrient composition, have not been carefully investigated in a controlled feeding study. Therefore, we will conduct an inpatient controlled feeding study in 20 overweight and obese adult men to investigate the changes in multi-organ insulin sensitivity and hepatic triglyceride content resulting from consuming two test diets for a pair of 3 week periods. The test diets will be implemented in a randomized, crossover design with each test diet following a 1 week run-in period of inpatient controlled feeding of a standard metabolic diet. The test diets will be matched for calories, macronutrient composition, sugar, fiber, and sodium, but one diet will be composed of ultra-processed foods whereas the other diet will be unprocessed foods. Multi-organ insulin sensitivity and hepatic triglyceride content will be measured at the end of each 1 week run-in period as well as at the end of each 3 week test diet period.