The Plasticity of Taste Function Links the Appetitive Taste of Fats with Obesity

Taste Responses in the Nucleus of the Solitary Tract of Awake Obese Rats Are Blunted Compared With Those in Lean Rats

Taste perception changes with obesity but the underlying neural changes remain poorly understood. To address this issue, we recorded taste responses from single cells in the nucleus tractus solitarius (NTS, the first synapse in the central gustatory circuit) in awake, diet-induced obese [(DIO; ≥ 8 weeks on a high-energy diet (45%fat, 17% sugar; HED)], and lean rats. Rats were implanted with a bundle of microelectrodes in the NTS and allowed to recover. Water-deprived rats were allowed to freely lick various tastants in an experimental chamber. Taste stimuli included an array of sapid stimuli dissolved in artificial saliva (AS). Each taste trial consisted of five consecutive licks followed by five AS licks presented on a VR5 schedule. Results showed that taste responses (n = 49 for DIO; n = 74 for lean rats) in NTS cells in DIO rats were smaller in magnitude, shorter in duration, and longer in latency that those in lean rats. However, there were proportionately more taste-responsive cells in DIO than in lean rats. Lick coherence in DIO rats was significantly lower than in lean rats, both in taste-responsive, and lick-related cells (n = 172 in lean; n = 65 in DIO). Analyses of temporal coding showed that taste cells in DIO rats conveyed less information about taste quality than cells in lean rats. Collectively, results suggest that a HED produces blunted, but more prevalent, responses to taste in the NTS, and a weakened association of taste responses with ingestive behavior. These neural adaptations may represent both negative effects and compensatory mechanisms of a HED that may underlie deficits in taste-related behavior associated with obesity.

Taste manipulation during a food cue-reactivity task: Effects on cue-elicited food craving and subsequent food intake among individuals with overweight and obesity

Food cue-reactivity tasks are used to induce and evaluate food cravings. Extant research has implicated the role of tasting foods in heightening cue-elicited food craving. The present study was the first to evaluate a taste manipulation during a food cue-reactivity task to optimize cue-elicited craving and predict food intake. Participants with overweight/obesity (N = 35; M age = 33.46 years [SD = 13.27]; M BMI = 32.91 kg/m2 [SD = 5.34]) engaged in one laboratory session and were randomized to a 'No Taste' or 'Taste' condition. All participants reported baseline food craving and observed two types of high-calorie food cues during a cue-reactivity task: photographic and real foods. The Taste group tasted real food cues and the No Taste group did not. Cue-elicited craving was assessed after the presentation of each food cue. Calorie intake of palatable foods was subsequently measured during a bogus taste test. Results indicated that cue-elicited craving to high-calorie foods was greater for the No Taste relative to the Taste group and that calorie intake was greater for the Taste relative to the No Taste group; both effects were nonsignificant, but of medium-size. Cue-elicited craving was significantly greater following exposure to high-calorie real food cues compared to photographic food cues. Results provide initial evidence that presenting high-calorie real (vs. photographic) food cues and forgoing taste manipulation during a food cue-reactivity task may optimize cue-elicited craving, and that taste manipulation could increase subsequent food intake. Future research should be conducted to replicate findings in larger samples with greater power to detect significant effects.