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  ORIGINAL ARTICLE Chilli consumption and the incidence of overweight andobesity in a Chinese adult population Z Shi 1 , M Riley 2 , AW Taylor 1 and A Page 1 BACKGROUND:  The frequency of spicy food intake has recently been associated with a reduced risk of mortality in the Chinesepopulation. This study aimed to prospectively examine the association between chilli intake and the incidence of overweight/ obesity in a Chinese adult population. METHODS:  Adults aged 20  –  75 years in the China Health and Nutrition Survey were followed between 1991 and 2011. Dietary datawere collected during home visits using a 3-day food record in 1991, 1993, 1997, 2000, 2004, 2006, 2009 and 2011. Cox regressionwas used in the analysis. Overweight/obesity was de fi ned as body mass index  ⩾ 25 kg m − 2 . RESULTS:  A total 12 970 adults were followed for a median of 9 years. During 126 884 person-years of follow-up, 3203 subjectsdeveloped overweight/obesity. The absolute incidence rate of overweight/obesity was 26.4, 22.3, 24.4 and 20.5 per 1000 person-years among those who consumed no chilli or 1  –  20, 20.1  –  50,  ⩾ 50.1 g per day, respectively. Chilli consumption was thereforeinversely associated with the incidence of overweight/obesity. After adjusting for age, gender, energy and fat intake, smoking,alcohol drinking and physical activity, those whose cumulative average chilli intake was 0, 1  –  20, 20.1  –  50 and ⩾ 50.1 g per day had ahazard ratio for overweight/obesity of 1.00, 0.81 (95% con fi dence interval=0.73  –  0.89), 0.77 (0.69  –  0.86) and 0.73 (0.63  –  0.84); P   for trend  o 0.001, respectively. There was no interaction between chilli intake and gender, income, education and residence(urban/rural) in relation to the risk of overweight/obesity. CONCLUSIONS:  Chilli intake is inversely associated with the risk of becoming overweight/obese in Chinese adults. International Journal of Obesity   (2017)  41,  1074  –  1079; doi:10.1038/ijo.2017.88 INTRODUCTION Worldwide, chilli is one of the most commonly used spices. 1  Thereis a large geographic and culture variation in chilli consumption.For example, chilli intake is higher in Asian than Europeancountries. 2 In China, more than 30% of adults consume spicy food,including chilli, daily. 3  The bene fi cial effects of chilli and its active componentcapsaicin have been reported including reducing mortality, 3 obesity 4 and rhinitis, 5 and increasing muscle strength. 6 However,a case  –  control study in Mexico found chilli consumption ispositively associated with stomach cancer. 7 Over the past several decades, a substantial amount of researchhas been conducted on the effects of chilli and the major pungentconstituent of chilli, capsaicin (8-methyl- N  -vanillyl-6-nonenamide),on energy balance. 4,8 Existing evidence from animal studies andsmall clinical trials suggest that chilli consumption may reduceenergy intake, increase energy expenditure and enhances f at oxidation, 4,8  –  11 especially among non-regular chilli consumers. 12  Thus chilli consumption may have the potential to assist in obesityprevention. However, the association between chilli consumptionand obesity has not been well studied in large populationstudies. Only one cross-sectional study has assessed the associa-tion between the frequency of spicy food consumption andobesity. 13 Contrary to the evidence from animal studies andclinical trials, in the China Kadoorie Biobank (CKB) study, thefrequency of spicy food consumption was shown to be positivelyassociated with overweight/obesity among half a million Chineseadults. 13 However, the study measured frequency of intake andother details of   ‘ hot spicy food ’  rather than collecting detailedfood intake information, in particular of chilli intake. An inverseassociation between spicy f ood consumption and mortality wasfound in the CKB cohort 3 independent of body mass index.Another cross-sectional study from China showed that preferencefor very hot chilli was inversely associated with insulin resistancebut this study did not adjust for body fatness. 14 Using data from the China Health and Nutrition Survey (CHNS),the aim of the current study was to prospectively examine theassociation between chilli consumption and incident of over-weight/obesity in a Chinese adult population. MATERIALS AND METHODS Study sample  The CHNS study is an ongoing open prospective household-based cohortstudy that includes nine provinces in China (representing 553 millionpeople). Nine waves of data collection (that is, 1989, 1991, 1993, 1997,2000, 2004, 2006, 2009 and 2011) have been conducted. 15,16  The surveyuses a multistage random-cluster sampling process to select samples inboth urban and rural areas. All the members in the selected householdwere invited to participate in the study, however, dietary intake in 1989only involved middle-aged adults. Since 1997, new households in the samecommunity joined the survey as replenishment samples to those lost tofollow-up owing to rural migration and city construction. The response ratebased on those who participated in 1989 and remained in the 2006 surveywas above 60%. The survey was approved by the institutional reviewcommittees of the University of North Carolina (USA) and the NationalInstitute of Nutrition and Food Safety (China). Informed consent wasobtained from all the participants. Between the 1991 and 2011 survey, 1 School of Medicine, University of Adelaide, Adelaide, SA, Australia and  2 Commonwealth Scienti fi c and Industrial Research Organisation (CSIRO), PO Box 10041, Adelaide, SA,Australia. Correspondence: Associate Professor Z Shi, School of Medicine, University of Adelaide, Level 7, SAHMRI, North Terrace, Adelaide, SA 5005, Australia.E-mail: Zumin.shi@adelaide.edu.auReceived 24 November 2016; revised 9 March 2017; accepted 19 March 2017; accepted article preview online 31 March 2017; advance online publication, 25 April 2017 International Journal of Obesity (2017)  41,  1074  –  1079 © 2017 Macmillan Publishers Limited, part of Springer Nature. All rights reserved 0307-0565/17 www.nature.com/ijo  there were 29 220 participants aged 20 years and older. We excludedthose without dietary intake ( n =13 793), had implausible energy intake(men: 4 6000 kcal or  o 800 kcal; women: 4 4000 or  o 600 kcal) ( n =651),pregnant women or breastfeeding ( n =798) or implausible body massindex ( o 14 or 4 45 kg m − 2 ,  n =38), and age 4 75 years ( n =2202) duringa survey year (otherwise included during other survey years). In total,18 611 participated in at least two waves of data collection includinginformation on chilli intake. After excluding those who were overweight/ obese at baseline ( n =5641), 12 970 participants were included in the  fi nalanalysis. Outcome variable: overweight/obesity Height and weight were measured at each wave. Overweight/obesity wasde fi ned as body mass index  ⩾ 25 kg m − 2 . Exposure variables: chilli intake At each wave, all foods and condiments in the home inventory, purchasedfrom markets or picked from gardens, and food waste, were weighed andrecorded by interviewers at the beginning and end of the 3-day foodconsumption survey. Individual dietary intake data were collected by atrained investigator conducting a 24 h dietary recall on each of the 3consecutive days. The dietary recall was supported by dietary records keptby the individual with the  fi nal dietary data including the type and amountof food, the type of meal and the place of consumption. Cooking oil andcondiments consumption for each individual in the household wasestimated using household intake weighted by individual energy intake.Detailed description of the dietary measurement has been publishedpreviously. 15  The dietary assessment method has been validated forenergy intake. The correlation coef  fi cient between the reported energyintake and total energy expenditure determined by the doubly labelledwater method was 0.56 ( P  o 0.01) for men and 0.60 ( P  o 0.01) for women. 17 Food consumption data were converted to nutrient intake using theChinese Food Composition Table.Chilli in China is consumed as fresh food as well as dried product. Wecalculated a cumulative average intake of chilli (sweet capsicum is notincluded) for each individual at each time period to reduce variation withinindividuals and to represent long-term habitual intake. 18 For example,the 1991 intake was used for the follow-up between 1991 and 1993, theaverage of the 1991 and 1993 intake was used for the follow-up between1997 and 2000 and so on.Habitual intake of spicy food was only asked in 2009 by the questions ‘ Do you like to eat hot pepper or spicy food? (i) No, (ii) sometimes ( ⩾ 2times per week), (iii) often (three to four times per week), (iv) usually ( ⩾ 5times per week), (v) unknown ’ ; and  ‘ What kind of spicy food do you like?(i) A little bit hot, (ii) moderate hot, (iii) very hot, (iv) unknown ’ . Covariates Detailed information on sociodemographic and lifestyle factors werecollected in each wave using a structured questionnaire. We included thefollowing constructed variables to re fl ect socioeconomic status: education(low: illiterate/primary school; medium: junior middle school; and high:high middle school or higher), per capita annual family income (recodedinto tertiles as low, medium and high), urbanisation levels 15 (recoded intotertiles as low, medium and high).Physical activity level (metabolic equivalent of task) was estimated onthe basis of self-reported activities (including occupational, domestic,transportation and leisure time physical activity) and duration using aCompendium of Physical Activities. Smoking status was categorised asnon-smokers, ex-smokers and current smokers.Blood sample measurement (in 2009 only) included fasting plasmaglucose and glycated haemoglobin. 19 C-reactive protein was measured inthe blood via the immunoturbidimetric method with Denka Seiken, Japanreagents. We de fi ned diabetes as fasting plasma glucose 4 7.0 mmol l − 1 ,glycated haemoglobin  4 6.5 or having known diabetes (self-reporteddoctor diagnosed). Hypertension was de fi ned as systolic blood pressureabove 140 mm Hg and/or diastolic blood pressure above 90 mm Hg orhaving known hypertension. Statistical analysis Chilli intake was recoded into four levels: non-consumers, 1  –  20, 20.1  –  50, ⩾ 50.1 g per day. The chi-square test was used to compare differences between groupsfor categorical variables and analysis of variance for continuous variables.A random effect model using xtreg command in Stata was used toassess the association between chilli intake and physical activity adjustingfor age, gender, energy intake and year of survey. We used Coxproportional hazards models with time-varying cumulative chilli consump-tion and covariates to compute hazard ratios. A set of models were used:model 1 adjusted for age, gender and energy intake; model 2 furtheradjusted for intake of fat, smoking, alcohol drinking, income, urbanisation,education and physical activity. Model 3 further adjusted for two dietarypatterns (traditional south pattern and modern pattern, determined usingfactor analysis based on our previous publication 20 ). Traditional southpattern is characterised by high intake of rice, pork and vegetables, andlow intake of wheat; a modern dietary pattern had high intake of fruit, soymilk, egg, milk and deep fried products.Cox proportional hazards assumptions were investigated by visualinspection of log  –  log plots generated by  stphplot   syntax in Stata, showingno deviations.In sensitivity analyses, we also used baseline chilli intake, or most recentchilli intake as the exposure variable. To assess the association betweencumulative chilli intake and weight change between 1991 and 2011among all participants (including those who were overweight/obese atbaseline), we used mixed-effect linear regression adjusting for covariatesthe same as model 3 mentioned above. All the analyses were performedusing STATA 14.1 (Stata Corporation, College Station, TX, USA). Statisticalsigni fi cance was considered when  P  o 0.05 (two-sided). RESULTS At baseline, participants with high chilli consumption had lowincome, were more physically active and less likely to havehypertension compared with non-consumers ( Table 1). Energyintake increased with the increase in chilli consumption. The age-and gender-adjusted mean intake of chilli was around 15 gper day between 1991 and 2011 (Supplementary Figure 1). Themedian portion size for chilli intake was 50 g. In each survey,around 30% of the participants consumed chilli during the 3 days.Among the chilli consumers, about 30% had chilli intake above50 g per day (data not shown). Compared with non-consumers,moderate consumers ( o 20 g per day) had a lower intake of energy but high consumers had a higher intake of energy(Supplementary Figure 2). Among chilli consumers, there was apositive association between chilli intake and energy intake.Cumulative chilli intake was positively associated with self-reported frequency intake and the preference for hot chilli in2009 (Supplementary Figure 3). Chilli consumption was positivelyassociated with the traditional dietary pattern (correlation coef  fi -cient 0.14,  P  o 0.001) but inversely associated with the moderndietary pattern (correlation coef  fi cient  − 0.06,  P  o 0.001; data notshown). Compared with non-consumers, moderate and highchilli consumption was associated with 3.32 (0.13, 6.51) and 4.27(0.80, 7.73) metabolic equivalent of task/week higher of physicalactivity level after adjusting for age, gender and year of survey(Supplementary Table 1).Overall, 12 970 adults were followed for a median of 9 years.During 126 884 person-years of follow-up, 3203 participantsdeveloped overweight/obesity. Chilli consumption was inverselyassociated with the incidence of overweight/obesity. The absoluteincidence rate of overweight/obesity was 26.4, 22.3, 24.4 and 20.5per 1000 person-years across levels of cumulative average chilliconsumption of 0, 1  –  20, 20  –  50,  4 50 g per day, respectively( Table 2). After adjusting for age, gender, energy and fat intake,smoking, alcohol drinking and physical activity, those who atechilli 0, 1  –  20, 20  –  50 and  4 50 g per day had a hazard ratio foroverweight/obesity of 1.00, 0.81 (95% con fi dence interval:0.73  –  0.89), 0.77 (0.69  –  0.86) and 0.73 (0.63  –  0.84) ( P   for trend o 0.001), respectively. After further adjusting for overall dietarypatterns, the association slightly attenuated but remainedstatistically signi fi cant. Adjusting for hypertension did not changethe above association (data not shown). There was no interaction Chilli intake and overweight/obesity among adultsZ Shi  et al  1075 © 2017 Macmillan Publishers Limited, part of Springer Nature. International Journal of Obesity (2017) 1074  –  1079  between cumulative average chilli intake and gender, income,education and residence (urban/rural) in relation to the risk of overweight/obesity. The above association was also found if weuse baseline chilli consumption and most recent chilli consump-tion as exposure variables.In the cross-sectional analysis of the 2009 data, 70% of theparticipants reported consuming spicy food. Compared with non-consumers of spicy food intake, consumers of spicy food waspositively associated with overweight/obesity (SupplementaryFigure 4). However, there was no dose  –  response relationshipbetween frequency/hotness of spicy food intake and overweight/ obesity.High cumulative chilli intake was inversely associated with bodyweight gain during follow-up using a fully adjusted mixed-effectlinear regression model (Supplementary Figure 5). DISCUSSION In this large prospective cohort study, we found that high intakeof chilli was inversely associated with the risk of overweight/ obesity independent of overall dietary pattern, energy intake andlifestyle factors. High chilli intake was positively associated withenergy intake. To the best of our knowledge, this is the  fi rstprospective study of chilli intake and the development of overweight/obesity using population data.Comparison with other studies The inverse association between chilli intake and overweight/ obesity in our study is consistent with most of the animal and small sample human studies 10,11,21 but is inconsistent with the fi ndings of the CKB study. 13 In the CKB study, the strength andfrequency of spicy food consumption was positively associated Table 1.  Baseline sample characteristics by baseline chilli intake categories Factor None 1 – 20 g per day 20.1 – 50 g per day  ⩾ 50.1 g per day  P -valueN   9221 1056 1336 1357Energy intake (kcal per day), mean (s.d.) 2417.9 (697.0) 2378.3 (706.6) 2486.7 (706.6) 2748.0 (754.6)  o 0.001Fat intake (g per day), mean (s.d.) 64.2 (36.2) 66.6 (35.9) 69.3 (40.2) 67.7 (43.3)  o 0.001Protein intake (g per day), mean (s.d.) 72.1 (23.3) 71.9 (24.2) 72.9 (23.2) 79.1 (26.3)  o 0.001Carbohydrate intake (g per day), mean (s.d.) 383.4 (138.6) 366.1 (139.3) 386.0 (133.8) 450.2 (151.6)  o 0.001 Traditional southern dietary pattern score, mean (s.d.)  − 0.1 (1.1) 0.1 (1.0) 0.2 (0.9) 0.3 (1.1)  o 0.001Modern dietary pattern score, mean (s.d.)  − 0.2 (0.9)  − 0.1 (1.0)  − 0.3 (0.8)  − 0.6 (0.8)  o 0.001Age (years), mean (s.d.) 40.5 (15.4) 39.0 (15.0) 39.4 (14.9) 39.1 (14.4)  o 0.001BMI (kg m − 2 ), mean (s.d.) 21.2 (2.0) 21.1 (2.0) 21.0 (2.0) 21.1 (2.0) 0.014 BMI status  0.90Underweight (BMI o 18.5 kg m − 2 ) 9.9% 10.6% 10.3% 10.2%Normal (18.5 ⩾  BMI and  o 25 kg m − 2 ) 90.1% 89.4% 89.7% 89.8% Sex   0.005Men 49.3% 49.2% 51.1% 54.3%Women 50.7% 50.8% 48.9% 45.7% Income  o 0.001Low 30.1% 29.4% 29.7% 37.4%Medium 32.9% 31.2% 31.9% 34.9%High 37.0% 39.4% 38.4% 27.7% Education  o 0.001Low 46.4% 42.9% 44.0% 53.9%Medium 32.9% 29.0% 33.0% 28.5%High 20.7% 28.1% 23.0% 17.6%Hypertension 10.2% 10.1% 8.0% 7.5% 0.004Diabetes (baseline in 2009 only,  n = 672; 458, 83, 74, 57) 7.4% 7.2% 8.1% 12.3% 0.64 Urbanisation  o 0.001Low 42.6% 33.6% 37.9% 51.1%Medium 28.3% 33.0% 32.3% 29.4%High 29.1% 33.4% 29.7% 19.5% Smoking  0.004Non-smoker 65.8% 64.7% 61.4% 63.4%Ex-smokers 1.9% 1.6% 1.3% 2.7%Current smokers 32.4% 33.7% 37.2% 33.9% Sleep duration (hours per day; baseline in 2004 onwards,  n =2425; 1553,242, 246, 204) 0.4107 – 9 79.7% 81.0% 83.3% 81.9% ⩽ 6 7.6% 7.0% 6.1% 5.9% ⩾ 10 12.7% 12.0% 10.6% 12.3%Physical activity (MET, hours per week), mean (s.d.) 204.3 (171.4) 198.7 (168.4) 212.1 (190.3) 214.6 (174.7) 0.061 Abbreviations: BMI, body mass index; MET, metabolic equivalent of task. Chilli intake and overweight/obesity among adultsZ Shi  et al  1076 International Journal of Obesity (2017) 1074  –  1079 © 2017 Macmillan Publishers Limited, part of Springer Nature.  with adiposity. However, the  fi ndings may be confounded by thecross-sectional study design and the lack of actual chilli intakedata. A Google search using  ‘ chilli ’  and  ‘ weight loss ’  in Chineseyielded over 400 000 results suggesting a public perception thateating chilli assists with losing weight. Similar to the  fi ndings of the CKB study, 13 using 2009 cross-sectional data, we also found apositive association between spicy food intake and overweight/ obesity. In a recent study from CKB, it had been shown thatspicy food consumption was inversely associated with the risk of mortality. 3 Consistent with our  fi ndings, a previous study usingdata from CHNS showed that preference for hot chilli wasinversely associated with insulin resistance. 14  Thus, a reversecausation mechanism seems likely in a cross-sectional study of chilli intake and obesity: people with overweight/obesity mayincrease their intake of chilli to manage their body weight. In ourcross-sectional analyses, no association was found betweenpreference for hot food and being overweight or obese. Thissuggests that preference for spicy food may not be a goodindicator to study the association between chilli consumption andobesity.Potential explanations and mechanisms of   fi ndingsIn our study, chilli consumption was positively associated withthe traditional dietary pattern but inversely associated with themodern dietary pattern. Adjusting for overall dietary patternsattenuated the association between chilli intake and the risk of overweight/obesity but the association remained strong andsigni fi cant. It suggests that the association between chilli intakeand overweight/obesity is independent of overall dietary patterns.Adding chilli to a high carbohydrate breakfast decreased thedesire to eat and hunger before lunch in 13 Japanese women, 11 resulting in reduced energy intake. The effect of chilli on energyintake was associated with an increase in the ratio of sympathetic:parasympathetic nervous system activity in 10 Caucasian men. 11 In another study of eight Caucasian adult males, the acute effectof red pepper (in combination with caffeine) on reducing energyintake was much greater than its concurrent ef fect on increasingenergy expenditure (3690 vs 320 kJ per day). 21 In our study, the association of chilli intake and overweight/ obesity is independent of energy intake. In fact, there was apositive association between high chilli intake and energy intake.Compared with non-consumers, mean energy intake was greaterby more than 200 kcal per day in individuals who consumedmore than 50 g per day of chilli. Although, physical activitywas higher in the high chilli consumers compared with non-consumers, the increased levels of physical activity could not fullyexplain the energy intake difference. This association may be morethan the often observed increase of all dietary components withincreasing energy intake. Furthermore, vegetables are often stirfried with vegetable oil in China. A positive association betweenvegetable-rich food pattern and vegetable oil consumption hasbeen reported. 22 In the current study, individuals with chilli consumption below20 g per day and above 50 g per day had reduced and increasedenergy intake, respectively compared with non-consumers.In humans, it has been demonstrated that dietary capsaicinenhances anorexigenic sensations such as satiety and fullness. 23,24 Although the exact mechanism of action is unknown, there areseveral physiological processes that could be involved. Forexample, gastrointestinal vagal afferents relay information onthe quantity and type of nutrients consumed, and have animportant role in the short-term control of food intake andmeal size. 25  These vagal afferents express the capsaicin-sensitivetransient receptor potential vanilloid channel 1 and the sensitivityof these afferents is enhanced by capsaicin or capsaicinanalogues. 26,27 However, capsaicin can also de-sensitise transientreceptor potential vanilloid channel 1. 28  Therefore, we postulatethat at low levels of capsaicin intake, there is sensitisation of vagal Table 2.  Hazard ratio (95% con fi dence interval) for incident overweight/obesity by chilli intake levels Chilli intake (g per day)None 1  –  20 20.1  –  50  ⩾ 50.1  P  for trend Cumulative average chilli intake Cases 1842 596 494 271Person-years 69 697 23 519 20 539 13 129Incident rate (per 1000) 26.4 25.3 24.1 20.6Model 1 1.00 0.78 (0.71 – 0.86) 0.76 (0.68 – 0.84) 0.69 (0.61 – 0.79)  o 0.001Model 2 1.00 0.81 (0.73 – 0.89) 0.77 (0.69 – 0.86) 0.73 (0.63 – 0.84)  o 0.001Model 3 1.00 0.81 (0.73 – 0.90) 0.81 (0.73 – 0.91) 0.82 (0.71 – 0.94) 0.001 Baseline chilli intake Cases 2297 248 316 342Person-years (1000) 8871 983 1318 1517Incident rate (per 1000) 25.9 25.2 24.0 22.6Model 1 1.00 0.96 (0.84 – 1.10) 0.90 (0.80 – 1.01) 0.82 (0.73 – 0.92)  o 0.001Model 2 1.00 0.96 (0.83 – 1.11) 0.94 (0.82 – 1.06) 0.87 (0.77 – 0.99) 0.003Model 3 1.00 0.96 (0.84 – 1.11) 0.98 (0.86 – 1.11) 0.94 (0.83 – 1.06) 0.098 Most recent chilli intake Cases 2296 270 357 280Person-years (1000) 88 132 10 419 14 192 14 142Incident rate (per 1000) 26.1 25.9 25.2 19.8Model 1 1.00 0.94 (0.83 – 1.07) 0.90 (0.80 – 1.01) 0.71 (0.63 – 0.80)  o 0.001Model 2 1.00 0.95 (0.83 – 1.09) 0.94 (0.83 – 1.06) 0.71 (0.62 – 0.82)  o 0.001Model 3 1.00 0.97 (0.84 – 1.11) 0.99 (0.88 – 1.12) 0.79 (0.69 – 0.91) 0.008 Model 1 adjusted for age, gender and energy intake. Model 2 further adjusted for intake of fat, smoking, alcohol drinking, income, urban, education andphysical activity. Model 3 further adjusted for dietary patterns 20 (traditional south pattern is characterised by high intake of rice, pork and vegetables, and lowintake of wheat; a modern dietary pattern had high intake of fruit, soy milk, egg, milk and deep fried products). All the adjusted variables are treated as time-varying covariates. Chilli intake and overweight/obesity among adultsZ Shi  et al  1077 © 2017 Macmillan Publishers Limited, part of Springer Nature. International Journal of Obesity (2017) 1074  –  1079
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