Dietary obesity and exercise in young rats

Area of Science:

• Physiology
• Nutrition Science
• Animal Models

Background:

• Understanding the impact of diet and exercise on energy balance is crucial for metabolic health.
• Investigating how high-energy diets and physical activity influence body composition and metabolic rates provides insights into weight management.
• Rats are commonly used models to study the complex interplay between food intake, energy expenditure, and body composition.

Purpose of the Study:

• To investigate the effects of a high-energy (HE) diet and daily swimming exercise on food intake, body weight, body composition, resting metabolic rate (RMR), and the thermic effect of food (TEF) in young rats.
• To determine how age and sex influence the metabolic and body composition responses to HE feeding and exercise.
• To assess the long-term effects of HE diet consumption and subsequent switching to a standard diet on energy balance parameters.

Main Methods:

• Young rats were divided into groups fed either a high-energy (HE) diet or a standard chow diet.
• One group of rats was subjected to daily forced swimming as a form of exercise.
• Measurements included food intake, body weight, body composition, RMR, and TEF.
• HE-fed rats were switched to lab chow at 104 days of age to observe post-diet switch effects.

Main Results:

• HE feeding generally led to increased food intake, body weight, and body fat, with a slight decrease in TEF compared to chow feeding.
• Exercise (swimming) resulted in lower body weight, reduced leanness, and higher RMR and TEF compared to sedentary controls.
• The impact of exercise was more pronounced in males, while the effects of the HE diet were greater in females.
• After switching HE-fed rats to chow, sedentary rats returned to control body weights, but exercised rats did not, and both HE groups remained fatter than controls.

Conclusions:

• Both high-energy diets and exercise significantly alter energy balance, body weight, and composition in rats.
• Sex and age play a role in modulating the responses to dietary energy density and physical activity.
• The metabolic and body composition changes induced by a high-energy diet can have persistent effects, even after returning to a standard diet, particularly in exercised individuals.