Changes in pattern of macronutrient intake during aging in male and female rats

Transversal and longitudinal studies of the natural patterns of food intake were made in male (n = 65) and female (n = 52) Lou rats, from 4 to 34 months of age. The efficiency of body weight control, especially for females, seems to be a main feature of this strain of rat: these rats are small eaters, have lighter body weight, show no development of obesity with age, and have a longer life expectancy than other common strains of rat. A better adaptation to feeding schedules was shown by female groups throughout the experiments. Moreover, an increased consumption for the oldest animals (from 28 months) enables them to keep their body weight constant up to age 34 months, whereas the male rats gradually lost weight with old age (from 28 months). When male and female rats of different age groups were allowed to choose their diet from pure macronutrient sources (protein, fat, and carbohydrate), an age-related shift of preferences from carbohydrate to fat diets was evidenced during daily energy intake. Protein intake also decreased according to age, earlier for males (around 21 months) than for females (34 months).