The Pavlovian power of palatable food: lessons for weight-loss adherence from a new rodent model of cue-induced overeating

Abstract

Objective: Relapsing to overeating is a stubborn problem in obesity treatment. We tested the hypothesis that context cues surrounding palatable food (PF) intake have the power to disrupt caloric regulation even of less PF. Context cues are non-food cues that are in the environment where PF is habitually eaten.

Design: Rats were conditioned to associate intake of Oreo cookies as the PF to cages with distinct context cues that differed from cues in cages where they were only given chow. PF naturally stimulated greater caloric intake. The rats were then tested in the PF cage with only chow available to determine whether the PF-paired cues, alone, could elicit overeating of plain chow.

Subjects: Non-food-deprived female Sprague-Dawley rats.

Measurements: Intake of plain chow under PF-paired cues vs chow-paired cues was compared. This was also measured in tests that included a morsel of PF as a priming stimulus. We also controlled for any effect of binge-prone vs binge-resistant status to predict cued-overeating.

Results: Rats consumed significantly more chow when exposed to context cues paired earlier with PF than with chow (P<0.01). This effect occurred using various cues (for example, different types of bedding or wallpaper). The effect was strengthened by priming with a morsel of PF (P<0.001) and was unaffected by baseline differences in propensity to binge on PF.

Conclusion: Context-cues associated with PF intake can drive overeating even of a less PF and abolish the ability of rats to compensate for the calories of a PF primer. Just as drug-associated context cues can reinstate drug-addiction relapse, PF-paired cues may trigger overeating relapses linked to weight regain and obesity. This model should help identify the reflex-like biology that sabotages attempts to adhere to healthy reduced calorie regimens and call greater attention to the cue-factor in the treatment of binge eating and obesity.

Figure 1

The mean amount of chow and Oreo cookie kcals ingested in the first 4 hrs of dark across four feeding tests used to determine binge-eating prone (BEP) from binge-eating resistant (BER) rats. BEPs ate more of the highly palatable food (cookies) than did BERs; **p<0.01 (and at each feeding test, **p<0.01 per test).

Figure 2

Amount of chow consumed when rats were placed in their home cage with only chow vs. in a cage previously associated with cookies in addition to chow (Cookie Cage) without counterbalancing context elements for each food condition. A) Intake of chow in each cage in the first 4 hrs; ns. B) Intake of chow in each cage over a 24 hr period; **p<0.01 chow intake in Cookie Cage vs. home cage. C) Intake of chow in each cage following a 2 g (10 kcal) preload of cookie as the palatable food (PF) “trigger” over 4 hrs; ***p<0.001 in Cookie vs. home cage. D) PF-triggered intake of chow in each cage over 24 hrs; ***p<0.001 in Cookie vs. home cage. Because there was no effect of group status (BEP vs. BER), both groups are represented in the bar graphs.

Figure 3

Amount of chow consumed over 4 hrs when rats were placed in a cage previously associated only with chow (Chow Cage) vs. in a cage previously associated with cookies in addition to chow (Cookie Cage) with context elements counterbalanced for each food condition. A) Intake of chow in each cage with and without a 2 g (10 kcal) piece of cookie as the palatable food (PF) “trigger”; ***p<0.001 main effect of PF-trigger to increase chow intake; **p<0.01 main effect of Cookie Cage to increase chow intake. B) Duplication of graph A but without the PF kcals shown to highlight the compensatory decrease in chow intake after a PF preload but only when rats were in the Chow Cage (**p<0.01). In the Cookie Cage, chow intake was greater than in the Chow Cage (***p<0.001) and there was no compensatory decrease in intake following the PF-trigger preload (ns).

Figure 4

A) Amount of PF-triggered chow consumed when rats were retested for context-cued overeating after Exp. 3 (Fig. 3) with no additional re-exposure to PF in the Cookie Cage and chow in the Chow Cage (reconditioning; instead rats spent 2 days in home cages prior to this retest); *p<0.05 greater chow intake in the Cookie Cage vs. Chow Cage. B) Amount of PF-triggered chow consumed when rats were retested for context-cued overeating after a short period of re-conditioning to PF in the Cookie cage and chow in the Chow Cage (reconditioning); **p<0.01 greater chow intake in the Cookie Cage vs. Chow Cage.