Elsevier

Physiology & Behavior

Volume 139, February 2015, Pages 80-88
Physiology & Behavior

Effects of long-term cycling between palatable cafeteria diet and regular chow on intake, eating patterns, and response to saccharin and sucrose

https://doi.org/10.1016/j.physbeh.2014.11.006Get rights and content

Highlights

  • Rats cycled between a cafeteria diet and chow develop binge-like eating behavior

  • Cycled rats withdrawn from cafeteria diet ate less of a novel biscuit than chow rats.

  • Cafeteria-fed and cycled rats ‘wanted’ saccharin less than chow-fed rats.

  • Chow-fed rats and cycled rats ‘liked’ sucrose more than cafeteria-fed rats.

  • These findings in rats may have important implications for yo-yo dieting in people.

Abstract

When exposed to a diet containing foods that are rich in fat and sugar, rats eat to excess and gain weight. We examined the effects of alternating this diet with laboratory chow on intake of each type of diet, the eating elicited by a palatable food (biscuits), and the drinking elicited by sweet solutions that did (sucrose) or did not (saccharin) contain calories. Each week for 13 weeks, cycled rats were provided with the cafeteria diet for three successive days/nights and the chow diet for the remaining four days/nights, whereas other rats received continuous access to either the cafeteria or the chow diets. On each of the 13 weeks, cycled rats ate more across the first 24 hour exposure to the cafeteria diet than rats continuously fed this diet. In contrast, cycled rats ate less across the first 24 hour exposure to the chow diet than rats continuously fed this diet and ate less when presented a novel palatable biscuit than chow-fed rats. The three groups exhibited similar licks per cluster to saccharin, but cafeteria-fed and cycled rats showed fewer clusters than chow-fed rats. In contrast, chow-fed rats and cycled rats exhibited more licks per cluster to sucrose than cafeteria-fed rats, but all three groups had a similar number of clusters. The results were discussed in relation to the effects of diet cycling on eating patterns, body weight, and ‘wanting’ and ‘liking’. These findings with rats may have important implications for yo-yo dieting in people.

Introduction

The overconsumption of energy-rich foods is thought to play a major role in the current obesity epidemic [1], [2]. One reason why energy-rich foods are eaten to excess is that they are hedonically pleasant [3]. The pleasure of eating such foods is also a reason why people find it difficult to refrain from eating them when trying to lose weight [4], [5]. Moreover, refraining from eating such foods can elicit stress, and, in turn, eating energy-rich foods can alleviate stress [6], [7], [8]. These relations between overconsumption of hedonically attractive foods and weight gain, the stress produced by dieting, and the alleviation of this stress by consumption of such foods, characterize many people in western society. The long-term effects of this pattern of eating, so-called “yo-yo” dieting [9], are unclear. Some studies have reported that such diet cycling is associated with increased risk of binge-eating and psychopathology, as well as a slowed metabolic rate [10]. Others have failed to find a link between diet cycling and adverse health effects [11], [12].

The long-term effects of diet cycling in rodents are also unclear. Again, some studies have found that cycling between low- and high-calorie diets results in binge-eating when the animals are shifted to the high calorie diet, as well as increased weight, fat intake, and ghrelin levels, relative to continuous access to a high-calorie diet [13], [14], [15], [16]. Other studies have reported that a history of diet cycling and the accompanying changes in body weight do not lead to obesity, decreased lifespan, changes in metabolic rate, or chronically elevated blood pressure [14], [17], [18], [19], [20]. Although much is still uncertain regarding the long-term effects of “yo-yo” dieting, two consistent findings in rodent models are that withdrawal from a palatable energy-rich diet produces stress, and that a return to the energy-rich diet produces overconsumption or ‘binging’ [21], [22]. However, little is known about the characteristics of eating across diet cycling.

The present study used rats to study the effects of cycling between a chow diet and a cafeteria diet containing many of the energy-rich foods eaten by people. There were three aims. The first was to examine whether cycling between the two diets altered intake of each: specifically, whether the cycled rats ate more when shifted to the cafeteria diet than rats continuously fed this diet but ate less when shifted to chow than those continuously fed this diet. The second aim was to determine whether the effect of shifting rats from the cafeteria diet to chow was specific to chow by comparing their intake of a novel palatable food (biscuits) with that of rats continuously fed chow. The final aim was to determine whether cycling rats between cafeteria and chow altered their ingestive responses to palatable sweet solutions that did (sucrose) or did not (saccharin) contain calories. Fig. 1 shows the experimental timeline.

Section snippets

Subjects

The subjects were 36 experimentally naïve male Sprague Dawley rats, obtained from a commercial supplier (Animal Resource Centre, Perth, Australia), aged 6–8 weeks and weighing 240–280 g upon arrival. They were housed in plastic boxes (22 cm height × 65 cm length × 40 cm width) with four rats per box, in a climate controlled room (22 °C) on a 12-hr reverse light/dark (lights off 9.00 am–lights on 9.00 pm) cycle. Rats were housed four per box due to ethical requirements to avoid any stress produced by

Weekly energy intake and body weight

Fig. 2 shows 24 h energy intake (kJ) measured during the first 24 h of each diet switch in Group Cyc and on the equivalent days for Groups Caf and Chow. The figure shows that Group Caf consumed more than Group Chow, and, more importantly, that Group Cyc consumed more than Group Caf when switched to the cafeteria diet, but less than Group chow when switched to chow diet. The first analysis confirmed that Group Caf consumed more kJs than Group Chow, averaged across all the measurements, F (1, 4) = 

Discussion

This experiment used rats to study the effects of the so-called yo-yo dieting [9], [10]. Many people in developed, and increasingly in non-developed, countries eat a diet that contains foods rich in fat and sugar. People like such foods, select them in preference to foods that are low in fat or sugar, and are likely to eat them to excess. The excessive consumption of such foods, in combination with a sedentary lifestyle, results in weight gain, even obesity, and a range of adverse health,

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