Food Decision-making In Obese Adults Under Different Homeostasis Conditions

Objective: Obesity is a global health problem.It is the unbalance of long time energy consumption and energy intake that cause obesity.Eating behaviors,especially food decisions,play a key role in obesity.There is a great deal of studies have shown that eating behaviors are largely influenced by the three systems.The homeostasis systemregulates the energy balance.The reward system is in charge of the non-homeostasis food intake.And the executive control system plays an important role in food-related self-regulation.However,there is very little literature to examine all three systems at the same time.Therefore,direct evidence of the influence of these three systems on feeding behavior is still lacked.The main purpose of this study is to explore how the reward system and self-control system of obese adults change under different energy homeostasis（hunger/satiety）,and how this change is related to food decision outcomes.Due to the homeostasis state is a complex system of central and peripheral mechanisms,in addition to the individual energy levels in the body（that is,the control of the state of hunger satiety）to control,this study also measured the participants in the saliva ghrelin and leptin levels as peripheral mechanism to measure the homeostasis system,discusses the hormone levels of steady-state peripheral relationship with brain regions activated.Methods:A mixed experimental design of 2 subjects type（normal/obese）and 2 energy homeostasis（hunger/satiety）was adopted in this study,in which subjects type was inter-subject variable and energy homeostasis was intra-subject variable.A total of 69 subjects were recruited for this study,including 30 obese adults and 39 healthy adults.Excluding subjects that did not meet the criteria,20 obese adults and 20 healthy adults were included in the analysis.Food decision paradigm needs to be completed: food health and taste rating task and food decision task.The food scoring task will make subjective evaluation on the health and delicious dimensions of food,and the evaluation results are healthy-unhealthy,good-tasting and bad-tasting,with a total of 4 food types.The food decision task asked participants to evaluate whether to choose a food.Finally,according to the evaluation results of the three tasks,select-health-unpalatable and reject-unhealthy delicious were defined as successful self-control decisions,and the successful self-control trials were included in f NIRS analysis.Participants were asked to fast for 17 hours before the test,which began with saliva samples to measure leptin and ghrelin levels,followed by a food decision task.After the task,the subjects were given a standardized lunch（total energy 600kcal）,which was drunk within15 minutes.After drinking,take a 15-minute rest to sample saliva again and perform food decision tasks.Results: Behavioral results showed that: 1)The health score of normal adults was significantly higher than that of obese adults,and the score of hungry adults was significantly higher than that of satiated adults.2)The score of palatable taste in the hungry state was significantly higher than that in the full state,and there was no significant difference in the score of palatable taste between normal and obese adults.3)The proportion of successful self-control decision was higher in normal adults,and successful self-control decision was not affected by steady-state conditions.4)In the hungry state,the proportion of unhealthy and delicious food was significantly higher than that in the full state;5)In the state of hunger,there was no significant difference in the weight of health score on decision-making results between obese adults and normal adults;In the satiety state,the weight of normal adults was significantly higher than that of obese adults.Results of biochemical indexes showed that 1)The level of ghrelin in hungry state was significantly higher than that in satiated state,and the level of ghrelin in obese adults was significantly higher than that in normal adults.2)Leptin level in hungry state was significantly lower than that in satiety state,and leptin level in obese adults was significantly lower than that in normal adults.The results of brain imaging showed that: 1)The OFC activation level of obese adults was significantly higher than that of normal adults,and the OFC activation level was not regulated by homeostasis.2)The activation level of dl PFC in normal adults was significantly higher than that in obese adults.The activation level of dl PFC in obese adults was not regulated by homeostasis,and the activation level of dl PFC in normal adults was higher when they were full.3)The activation of brain regions in PFC was independent of individual ghrelin and leptin levels.Conclusion: In the condition of hunger,normal adult self control ability is reduced,the energy steady more interaction and reward system,improve the individual estimate of the reward value,make the individual tends to be based on the degree of delicious food to make decision from the bottom up,for obese adults,the reward system is damage,food is more vulnerable to temptation,leading to more unhealthy eating behaviors;Normal adults showed increased self-control when they were full.At the same time,the reward system values the reward attributes of food less,making individuals more inclined to make decisions based on self-control.However,for obese people,their dl PFC ability is impaired,so homeostasis cannot affect dl PFC,and self-control is always kept at a low level,leading to the failure of self-control in this group.