Executive Function Performance And Intervention In Overweight And Obesity Individuals

The prevalence of obesity and overweight is rising problematically in developed and developing nations worldwide.The World Health Organization reported that in 2014,more than 600 million adults were obese and over 1.9 billion were overweight.This fact has far-reaching and costly implications,because excessive weight contributes to the development of numerous diseases,including cardiovascular disease,diabetes,and some cancers,and it is a risk factor for psychiatric disorders such as depression and anxiety.Therefore,it is important to explore the risk factors of overweight and obesity.Theoretically,executive function could be related to overweight and obesity.Executive function refers to a series of high order cognitive processes needed when individuals controlling their own thinking and behavior.The dual process model argues that much of our behavior is determined by an interaction between the impulsive system and the executive control system.In the case of excessive weight,coupled with a strong automatic approach response to high-calorie food and food cues,people who show low levels of executive control are particularly susceptible to obesity-related behaviors and outcomes(e.g.,increased intake of fatty foods,weight gain),whereas those with effective cognitive control may be protected.From another perspective,some of the psychological and physical factors associated with overweight and obesity may also impair individuals'executive function.Obesity is significantly related to psychological factors such as weight stigma,negative childhood experiences and poor eating behaviors,which can impair cognitive abilities,including executive function.Furthermore,obese females may experience more of these adverse psychological factors than obese males.Therefore,cognitive abilities(i.e.,executive function)of obese females may be more adversely affected than that of obese males.Therefor,the relationship between obesity and executive function is moderated by sex.Finally,in terms of physiological factors,researchers suggested that obesity itself may impairs individuals'cognition,mainly due to the low-grade inflammation associated with obesity.In summary,this study designed five studies in two parts to examine executive function performance and intervention in overweight/obese individuals.Through two studies(Study 1 and study 2ab),the first part of this study attempted to determine the relationship between overweight/obesity and executive function(Study 1),explore moderation and mediation roles of sex and inflammation on this relationship,and revealed the performance and influencing factors of executive function in obese individuals.After determined the relationship between overweight/obesity and executive function,three studies in the second part of this study(Studies 3,4,and 5)attempted to train the executive function of overweight and obese individuals to intervene their high-calorie food consumption and weight.By conducting a meta-analysis,study 3 first investigated the effects of 66 cognitive training studies on individuals' eating behavior and body weight.Based on the results of study 3,study 4 used food-related inhibition training to intervene their high calorie food consumption,and compared the differences of the training effect between normal individuals and overweight/obese individuals.In study 5,using food-related inhibition training,longitudinal intervention was conducted in overweight/obese individuals to investigate the effects of this intervention on the evaluation of high-calorie foods(both behavioral and brain imaging)in overweight/obesity individuals and their weight.The innovations of this research are mainly as follows:(1)Different from the dominant reward theory in this field,this study suggested that executive function was also associated with overweight/obesity.(2)The factors affecting the relationship between obesity and executive function deficiency were explored in an exploratory way,and the role of low level inflammation as a biomarker between obesity and executive function was established,thus providing the first direct evidence for the two-way relationship between obesity and executive function deficiency.(2)For the first time,food-related inhibitory control intervention(one of the executive function subcomponents)were applied to overweight/obese individuals and investigated effects of this intervention on high-calorie eating behavior,high-calorie food evaluation and weight.In study 1,we synthesize the related literature by conducting a meta-analysis of studies comparing executive functions in overweight/obese individuals to normal weight controls.We identified 72 studies—with 4904 overweight/obese participants—that met our inclusion criteria.Effect sizes were analyzed using the robust variance estimation random effects meta-regression technique.It was found that obese participants showed broad impairments on executive function,including on tasks primarily utilizing inhibition,cognitive flexibility,working memory,decision-making,verbal fluency,and planning.overweight participants only showed significant deficits in inhibition and working memory.The only moderator of effects of obesity to emerge significant was the task used to assess the respective executive function,which moderated effects of obesity on working memory and decision-making.In sum,current evidence supports the existence of broad executive function deficits in obese individuals,and small inhibition and working memory deficits in overweight individuals.The results of Study 1 were further supported by data from Add Health(The National Longitudinal Study of Adolescent to Adult Health)database(N>10000),more importantly,study 2 further explored the factors affecting the relationship between obesity and insufficient executive function.To be specific,study 2a used data from Wave? of Add Health to verify the association between obesity and lower executive function and examine whether sex moderated this association.Executive function was assessed using a modified digit span backward task.As expected,similar to the result of study 1,when controlling for several important covariates(e.g.,smoking),we found that obesity was associated with a relative executive function deficit.More importantly,sex moderated this association,obesity was related to a relative executive function deficit in women,not men.Study 2b examined whether inflammation statistically mediated the relationship between obesity and executive function in a nationally representative dataset of U.S.adults from Wave ? of The National Longitudinal Study of Adolescent to Adult Health.Inflammation was quantified via C-reactive protein(CRP)level,and executive function was assessed using a modified digit span backward task.As expected,cross-sectional analyses showed that a body mass index(BMI)indicative of obesity—as well as greater BMI when BMI was analyzed continuously—and greater CRP were each related to lower executive function.Critically,we found that CRP levels statistically mediated the relationships between obesity/greater BMI and executive function,with CRP accounting for 44.1%of the variance explained in executive function by BMI.Moreover,these findings held both with and without controlling for relevant covariates,including demographic characteristics(e.g.,age),socioeconomic status,and behavioral factors(e.g.,smoking).In study 3,We examined 66 independent experiments that examined the effects of cognitive training aimed at reducing cognitive bias or improving executive control on eating behavior and weight loss.Overall,inhibition training,attention bias modification training,and episodic future thinking training significantly influenced eating behavior;however,approach/avoidance training did not significantly influence eating behavior.Moderator analyses indicated that the effect of inhibition training on eating behavior was moderated by training task and food novelty,the effect of approach/avoidance training was moderated by food type,and the effect of episodic future thinking training was moderated by type of episodic future thinking.Literature reviewed on cognitive training and weight loss provided preliminary support for the effects of food-specific inhibition training on weight loss from pre-intervention to post intervention.However,most of the included studies focused on short-term outcomes in normal-weight samples.Since study 3 found that inhibition training,especially food-related inhibition training,not only has an impact on the individual's eating behavior,but also may have an impact on body weight.And this study also focused on the effect of executive function intervention on overweight/obese individuals.Therefore,studies 4 and 5 focused on the influence of this intervention on the eating behavior and weight of overweight/obese individuals.Study 4 used food-related inhibition training to intervene eating behavior in overweight/obese individuals and investigated the differences of the training effect in overweight/obese individuals and normal weight individuals.Results showed that food-related inhibition training can be applied to overweight/obese individuals,who showed better task performance.However,this study found that food-related inhibition training did not affect the high-calorie food eating behavior of normal weight and overweight/obese individuals.Exploratory analysis showed that hunger could modulate the effect of food-related inhibition training on eating behavior.Food-related inhibition training can significantly reduce the consumption of target intervention food only when the participants'hunger is low.Study 5 conducted weekly longitudinal interventions to reduce the high-calorie food evaluations(behavioral and brain imaging)and body weight in overweight/obese individuals using food-related inhibition training in five weeks.Results showed that overweight/obese participants can be well adapted to the longitudinal intervention and almost all participants completed the intervention.At the behavioral level,intervention group showed a significant reduction on food evaluation(attractiveness and liking)compared to the control group.At the brain imaging level,intervention group showed significant reductions on the inhibitory control,reward,and attentional brain regions response to high-calorie food images versus low-calorie food images.Finally,no significant changes in BMI was observed in the intervention group.To sum up,this study explored the topic of executive function performance and intervention in overweight and obese individuals through two parts and five studies.Main results showed that(1)obese participants showed broad impairments on executive function,including on tasks primarily utilizing inhibition,cognitive flexibility,working memory,decision-making,verbal fluency,and planning.overweight participants only showed small significant deficits in inhibition and working memory.Task used to assess the respective executive function moderated effects of obesity on working memory and decision-making.(2)Gender and inflammation respectively played moderation and mediation roles on the association between obesity and executive function.(3)In cognitive interventions aimed to improving executive function or reducing cognitive biases,inhibition training,attention bias modification training,and episodic future thinking training significantly influenced eating behavior;however,approach/avoidance training did not significantly influence eating behavior.Moderator analyses indicated that the effect of inhibition training on eating behavior was moderated by training task and food novelty,the effect of approach/avoi dance training was moderated by food type,and the effect of episodic future thinking training was moderated by type of episodic future thinking.Literature reviewed on cognitive training and weight loss provided preliminary support for the effects of food-specific inhibition training on weight loss from pre-intervention to post intervention.(4)Food-related inhibition training could be applied to overweight and obese individuals,who showed better task performance.However,food-related inhibition training did not affect the eating behavior of normal weight and overweight/obese individuals.Hunger modulated the effect of food-related inhibition training on eating behavior.Food-related inhibition training can significantly reduce the consumption of target intervention food only when the participants' hunger is low.(5)Longitudinal food-related inhibition training reduced the evaluation of high-calorie food images(attractiveness and liking)in overweight/obese individuals,and they showed significant reductions on the inhibitory control,reward,and attentional brain regions response to high-calorie food images versus low-calorie food images.However,preliminary evidence from this study suggested that food-related inhibition training can not reduce the weight of overweight/obese individuals.Larger randomized controlled trials are needed in the future to verify the effect of food-related inhibition training on body weight.