Dietary modulation of ghrelin and leptin and gorging behavior after weight loss in the obese Zucker rat

Abstract

In this study, we measured ghrelin and leptin in obese Zucker rats after weight loss induced by calorie restriction using either a low-fat (LF) or high-energy palatable (HEPa) diet. After weight loss, the animals were refed lab chow and offered one hour-palatable test meals on the second and fifteenth days of refeeding. Both LF and HEPa rats lost 10% of their initial body weight (P!0 . 0001). Plasma ghrelin increased with calorie restriction in both groups (P!0 . 002) with a tendency to a higher increase in the HEPa group while plasma leptin decreased only in the LF group (P!0 . 01). Both groups ate the same quantity of chow during refeeding and both groups gorged on palatable diet during test meals at a very high constant intensity in HEPa rats. After one week of refeeding, ghrelin levels remained elevated in HEPa rats (C33 . 2%; P!0 . 001) while returning to baseline in LF rats. Plasma leptin remained low in LF rats. We conclude that weight loss on a palatable diet is possible if total energy intake is controlled. After stopping restriction, when a palatable diet is available, observed gorging might be dependent on specific ghrelin and leptin changes.

A Diet with Carbohydrates Eaten Primarily at Dinner: An Innovative, Nutritional Approach to End the Vicious Cycle of Abdominal Obesity

“…Decreased leptin levels following weight loss diets have been well documented in previous studies [3,4,8,34,35] and may be explained by reduced body fat mass. Reduced leptin serum concentrations during weight loss programs are commonly associated with a decline in satiety levels [3,4,35,36], as observed in our control group. In the experimental group, this expected satiety reduction did not occur.…”

“…A possible explanation is the higher insulin levels that occurred throughout the day in the control group who ate carbohydrates during daylight hours and the reported reciprocal relationship between insulin and ghrelin secretion [14,[39][40][41][42]. It was expected that ghrelin's overall increase in the experimental group would contribute to hunger sensations as the diet progressed, as has been described previously [8,36,40,43]; however, this was not the case and the experimental group reported higher levels of satiety. We propose that the change in ghrelin's curve to lower relative concentrations in the afternoon may contribute to the enhanced daytime satiety experienced by the experimental diet group.…”

“…On the contrary, at the end of the study, the experimental diet group had higher H-SSc in comparison to baseline. Previous studies with different diets reported that, during weight loss, leptin concentrations decreased, satiety levels were reduced, food intake was renewed, and a slow regain of body weight occurred [35][36][37]. It is obvious that dietary manipulations that maintain higher leptin concentrations through waking hours during weight loss process will be beneficial for dieters.…”

Caloric restriction

“…The decline in leptin appears to be partially dependent on the composition of the diet. When obese Zucker rats were restricted either using a low fat or a highly palatable diet both groups lost similar amounts of body fat (c 10% of body weight), but the decrease in leptin was significant only in the group given the low fat diet (Beck and Richy, 2009). CR markedly down-regulated resistin gene expression.…”

“…Combined with the slow rise in the levels during the initial phase of CR these data are consistent with the suggestion that the morphological changes in the stomach are the major cause of changes in the circulating levels of this hormone. For example, in obese Zucker rats, after CR using either a low-fat or high-energy palatable diet plasma ghrelin increased in both groups (p < 0.002) with a tendency to a higher increase in the rats fed the palatable diet (Beck and Richy, 2009). After one week of refeeding, ghrelin levels remained elevated in the rats that had been fed the palatable diet (+33.2%; p < 0.001) but returned to baseline in rats fed the low fat diet.…”