The effects of energy intake of four different feeding patterns in rats

Abstract

Energy intake can affect the metabolism. But it is not very clear that how and to what degree the metabolism can be changed by energy intake quantity and change. Here we applied four feeding patterns in male Sprague-Dawley rats--normal ad libitum diet (NFal), high-fat diet (HFal), caloric restriction (CR) after HFal (HFal-NFcr), and refeeding from CR to ad libitum (HFal-NFcr-NFal). Food intake and body weight, along with fat mass, insulin sensitivity, fasting plasma insulin, and glucose level were used to calculate the energy efficiency and compared the quantitative effects of energy intake. Energy intake changed little in NFal or HFal group; while it changed greatly and suddenly in HFal-NFcr or HFal-NFcr-NFal group. All the parameters we detected were different between these four feeding patterns. Excess of energy intake from high-fat diet induced adverse outcomes with low energy efficiency. CR reversed the impairment of high-fat diet with very high energy efficiency in a short period. However, dramatic response with high energy efficiency induced by recovery to feeding ad libitum after CR, which was possible harmful to health. In conclusion, energy intake quantity and change are key determinants of metabolism. Different energy intake quantity and change affect body weight, white adipose tissue weight, insulin sensitivity, etc. at different degrees and speeds because of different energy efficiency.

Keywords: Energy efficiency; caloric restriction; fat mass; high-fat diet; insulin sensitivity; refeeding.

Figure 1

The groups, the average daily energy intake per rat (DEI), and body weight of the animal model. (a) The diagram of the animal model. Male Sprague–Dawley (SD) rats were assigned into four groups: NFal—feed ad libitum with normal chow diet (n = 28, 19, and 10 in phase I, II, and III, respectively), HFal—feed ad libitum with high-fat diet (n = 56, 19, and 10 in phase I, II, and III, respectively), HFal-NFcr—caloric restriction with normal chow diet after HFal for about two months (n = 18 and 9 in phase II and III, respectively) and HFal-NFcr-NFal—refeeding ad libitum with normal chow diet after CR for about two months (n = 10). A: for blood and fat pad, n = 4–5; B: for euglycemic–hyperinsulinemic clamp technique, n = 5. (b) The average daily energy intake per rat of the four groups in each week. The food intake per rat was measured once a week and the daily energy intake per rat was calculated as described in “Methods and Materials” section. *: P < 0.05 versus NFal at the same time point; #: P < 0.05 versus the start point of the same group. (c) The body weight of the four groups in each week. n = 9–56 as shown in Figure 1(a). *: P < 0.05 versus NFal at the same time point

Figure 2

The fat pad weight and insulin sensitivity at different time points in each group. (a) The left side epididymal fat pad weight (n = 4–5). (b) The insulin sensitivity was detected by euglycemic–hyperinsulinemic clamp technique and presented with glucose infusion rate (GIR). (n = 5) NFal—feed ad libitum with normal chow diet, HFal—feed ad libitum with high-fat diet, HFal-NFcr—caloric restriction with normal chow diet after HFal for two months and HFal-NFcr-NFal—refeeding ad libitum with normal chow diet after CR for two months. 4 M, 6 M, and 8 M: the age of four, six, and eight months old. **: P < 0.01 versus other groups at the same age; ##: P < 0.01 versus the same groups at different ages. All values are means ± S.E