Stephen Whybrow

Resistance and susceptibility to weight gain: Individual variability in response to a high-fat diet

An obesigenic environment is a potent force for promoting weight gain. However, not all people exposed to such an environment become obese; some remain lean. This means that some people are susceptible to weight gain (in a weight-promoting environment) and others are resistant. Identifying the characteristics of appetite control and food motivation in these two groups could throw light on the causes of weight gain and how this can be either treated or prevented. We have investigated the issue experimentally by identifying people who habitually consume a high-fat diet (greater than 43% fat energy). These individuals have been termed high-fat phenotypes. We have compared individuals, of the same age (mean=37 years old) and gender (male), who have gained weight (BMI=34) or who have remained lean (BMI=22). The susceptible individuals are characterised by a cluster of characteristics including a weak satiety response to fatty meals, a maintained preference for high-fat over low-energy foods in the post-ingestive satiety period, a strong hedonic attraction to palatable foods and to eating, and high scores on the TFEQ factors of Disinhibition and Hunger. The analysis of large databases suggests that this profile of factors contributes to an average daily positive energy balance from food of approximately 0.5 MJ. This profile of characteristics helps to define the symptomatology of a thrifty phenotype.

Problems in identifying predictors and correlates of weight loss and maintenance: Implications for weight control therapies based on behaviour change

Weight management is a dynamic process, with a pre‐treatment phase, a treatment (including process) phase and post‐treatment maintenance, and where relapse is possible during both the treatment and maintenance.

Energy density, diet composition and palatability: influences on overall food energy intake in humans.

This paper considers the role of energy density (ED), diet composition and palatability in the control of energy intake (EI) in humans through several related considerations: (i) the relationship between ED and diet composition, (ii) the relationship between ED, diet composition and EI, (iii) the relationship between palatability and EI, (iv) the relationship between ED, palatability and EI, (v) the importance of postingestive factors in influencing palatability in the longer term, (vi) the contribution of sensory and nutritional factors to dietary hyperphagia and (vii) the implications these considerations have for people living their normal lives in their natural environment. The main factors influencing ED are the fat and water content of foods. Energy density does elevate EI, especially in short-term studies where it can account for >40% of the variance in EI. In real life, ED accounts for only approximately 7% of the variance in EI. This is because the determinants of EI are multifactorial and also because the short-term effects of ED on EI do not translate into the longer term. We argue that part of the longer term amelioration of short-term effects of ED on EI is due to learned compensation, based on the postingestive consequences of consuming familiar food that differ in ED. More energy-dense foods tend to be more palatable but we learn to consume them in smaller portion sizes. In the longer term, the perceived palatability of a food is strongly influenced by the postingestive consequences of eating it. This effect can override sensory factors alone. This implies that nutrient mimetics, if used continuously, would not be as efficacious as initially supposed and that their ad hoc use may undermine the stability of learned appetites and satieties for foods with different EDs and contribute to the poor weight control capability exhibited by consumers at large.

Weight outcomes audit for 34,271 adults referred to a primary care/commercial weight management partnership scheme

Objective: This project audited rate and extent of weight loss in a primary care/commercial weight management organisation partnership scheme. Methods: 34,271 patients were referred to Slimming World for 12 weekly sessions. Data were analysed using individual weekly weight records. Results: Average (SD) BMI change was –1.5 kg/m2 (1.3), weight change –4.0 kg (3.7), percent weight change –4.0% (3.6), rate of weight change –0.3 kg/week, and number of sessions attended 8.9 (3.6) of 12. For patients attending at least 10 of 12 sessions (n = 19,907 or 58.1%), average (SD) BMI change was –2.0 kg/m2 (1.3), weight change –5.5 kg (3.8), percent weight change –5.5% (3.5), rate of weight change –0.4 kg/week, and average number of sessions attended was 11.5 (0.7) (p < 0.001, compared to all patients). Weight loss was greater in men (n = 3,651) than in women (n = 30,620) (p < 0.001). 35.8% of all patients enrolled and 54.7% in patients attending 10 or more sessions achieved at least 5% weight loss. Weight gain was prevented in 92.1% of all patients referred. Attendance explained 29.6% and percent weight lost in week 1 explained 18.4% of the variance in weight loss. Conclusions: Referral to a commercial organisation is a practical option for National Health Service (NHS) weight management strategies, which achieves clinically safe and effective weight loss.

Effects of added fruits and vegetables on dietary intakes and body weight in Scottish adults

An increased consumption of fruits and vegetables (F&V) has been suggested as a way to limit, or even lower, energy and fat intakes. The present study examined the effects of incorporating F&V supplements into the diets of adults who reported consuming <240 g (three portions) of F&V per d on energy and fat intakes, and change in body weight, over 8 weeks using a randomised parallel design. Thirty-four males and twenty-eight females (age 42.6 (sd 11.1) years, BMI 23.7 (sd 2.7) kg/m(2)) were each provided with supplements of 0, 300 or 600 g F&V per d. Food, nutrient and energy intakes were measured before, during and at the end of the supplementation period using 7 d weighed records. Mean daily energy intakes were not different among the three groups before (P = 0.151) or during the supplementation periods (P = 0.407), although changes in energy intakes over the study period tended to be more positive with increasing amounts of F&V supplements (P = 0.078). There was no difference in changes of body weights during the study (P = 0.242). Carbohydrate (P < 0.001), sugar (P < 0.001), fibre (P < 0.001) and weight of food consumed (P = 0.022) increased in the treatment groups. There were no significant differences, or changes, in fat intakes among the three groups. Consumption of mandatory F&V supplements for 8 weeks produced beneficial changes in diet composition, but did not result in lower reported energy or fat intakes, and did not result in loss of body weight.

Developing a methodology for assigning glycaemic index values to foods consumed across Europe

There is growing evidence that the glycaemic index (GI) of the diet is important with respect to body weight and metabolic disease risk. However, research is limited by the paucity of GI values for commonly consumed carbohydrate‐rich foods in European countries. A new methodology has been developed for consistent assignment of GI values to foods across five European databases used in the Diogenes intervention study. GI values were assigned according to five decreasing levels of confidence (1) Measured values for specific foods; (2) Published values from published sources; (3) Equivalent values where published values for similar foods existed; (4) Estimated values assigned as one of three values representing low/medium/high GI ranges and (5) Nominal values assigned as 70, where no other value could be assigned with sufficient confidence. GI values were assigned to 5105 foods. In food records collected at baseline, the contribution to carbohydrate intake of foods assigned levels 1–2 ranged from 16% to 43% depending on country, and this increased to 53–81% including level 3 foods. The degree of confidence to assigned GI values differed across Europe. This standardized approach of assigning GI values will be made available to other researchers to facilitate further investigation into the effects of dietary GI on health.

Cognitive and weight-related correlates of flexible and rigid restrained eating behaviour.

OBJECTIVES Examine the association between components of restrained eating, cognitive performance and weight loss maintenance. METHODS 106 women, all members of a commercial slimming organisation for at least 6 months (mean±SD: 15.7±12.4 months), were studied who, having lost 10.1±9.7 kg of their initial weight, were hoping to sustain their weight loss during the 6 month study. Dietary restraint subcomponents flexible and rigid restraint, as well as preoccupying cognitions with food, body-shape and diet were assessed using questionnaires. Attentional bias to food and shape-related stimuli was measured using a modified Stroop test. Working memory performance was assessed using the N-back test. These factors, and participant weight, were measured twice at 6 month intervals. RESULTS Rigid restraint was associated with attentional bias to food and shape-related stimuli (r=0.43, p<0.001 resp. r=0.49, p<0.001) whereas flexible restraint correlated with impaired working memory (r=-0.25, p<0.05). In a multiple regression analyses, flexible restraint was associated with more weight lost and better weight loss maintenance, while rigid restraint was associated with less weight loss. CONCLUSIONS Rigid restraint correlates with a range of preoccupying cognitions and attentional bias to food and shape-related stimuli. Flexible restraint, despite the impaired working memory performance, predicts better long-term weight loss. Explicitly encouraging flexible restraint may be important in preventing and treating obesity.

Modelling the associations between fat-free mass, resting metabolic rate and energy intake in the context of total energy balance

Background:The relationship between body composition, energy expenditure and ad libitum energy intake (EI) has rarely been examined under conditions that allow any interplay between these variables to be disclosed.Objective:The present study examined the relationships between body composition, energy expenditure and EI under controlled laboratory conditions in which the energy density and macronutrient content of the diet varied freely as a function of food choice.Methods:Fifty-nine subjects (30 men: mean body mass index=26.7±4.0 kg m−2; 29 women: mean body mass index=25.4±3.5 kg m−2) completed a 14-day stay in a residential feeding behaviour suite. During days 1 and 2, subjects consumed a fixed diet designed to maintain energy balance. On days 3–14, food intake was covertly measured in subjects who had ad libitum access to a wide variety of foods typical of their normal diets. Resting metabolic rate (RMR; respiratory exchange), total daily energy expenditure (doubly labelled water) and body composition (total body water estimated from deuterium dilution) were measured on days 3–14.Results:Hierarchical multiple regression indicated that after controlling for age and sex, both fat-free mass (FFM; P<0.001) and RMR (P<0.001) predicted daily EI. However, a mediation model using path analysis indicated that the effect of FFM (and fat mass) on EI was fully mediated by RMR (P<0.001).Conclusions:These data indicate that RMR is a strong determinant of EI under controlled laboratory conditions where food choice is allowed to freely vary and subjects are close to energy balance. Therefore, the conventional adipocentric model of appetite control should be revised to reflect the influence of RMR.

Achieving dietary recommendations and reducing greenhouse gas emissions: modelling diets to minimise the change from current intakes

BackgroundAverage population dietary intakes do not reflect the wide diversity of dietary patterns across the population. It is recognised that most people in the UK do not meet dietary recommendations and have diets with a high environmental impact, but changing dietary habits has proved very difficult. The purpose of this study was to investigate the diversity in dietary changes needed to achieve a healthy diet and a healthy diet with lower greenhouse gas emissions (GHGE) (referred to as a sustainable diet) by taking into account each individual’s current diet and then minimising the changes they need to make.MethodsLinear programming was used to construct two new diets for each adult in the UK National Diet and Nutrition Survey (n = 1491) by minimising the changes to their current intake. Stepwise changes were applied until (i) dietary recommendations were achieved and (ii) dietary recommendations and a GHGE target were met. First, gradual changes (≤50 %) were made to the amount of any foods currently eaten. Second, new foods were added to the diet. Third, greater reductions (≤75 %) were made to the amount of any food currently eaten and finally, foods were removed from the diet.ResultsOne person out of 1491 in the sample met all the dietary requirements based on their reported dietary intake. Only 7.5 and 4.6 % of people achieved a healthy diet and a sustainable diet, respectively, by changing the amount of any food they currently ate by up to 50 %. The majority required changes to the amount of each food eaten plus the addition of new foods. Fewer than 5 % had to remove foods they ate to meet recommendations. Sodium proved the most difficult nutrient recommendation to meet. The healthy diets and sustainable diets produced a 15 and 27 % reduction in greenhouse gas emissions respectively.ConclusionsSince healthy diets alone do not produce substantial reductions in greenhouse gas emissions, dietary guidelines need to include recommendations for environmental sustainability. Minimising the shift from current dietary intakes is likely to make dietary change more realistic and achievable.

An evaluation of the IDEEA activity monitor for estimating energy expenditure

Objective estimates of activity patterns and energy expenditure (EE) are important for the measurement of energy balance. The Intelligent Device for Energy Expenditure and Activity (IDEEA) can estimate EE from the thirty-five postures and activities it can identify and record. The present study evaluated the IDEEA systems estimation of EE using whole-body indirect calorimetry over 24 h, and in free-living subjects using doubly-labelled water (DLW) over 14 d. EE was calculated from the IDEEA data using calibration values for RMR and EE while sitting and standing, both as estimated by the IDEEA system (IDEEA(est)) and measured by indirect calorimetry (IDEEA(meas)). Subjects were seven females and seven males, mean age 38·1 and 39·7 years, mean BMI 25·2 and 26·2 kg/m2, respectively. The IDEEA(est) method produced a similar estimate of EE to the calorimeter (10·8 and 10·8 MJ, NS), while the IDEEA(meas) method underestimated EE (9·9 MJ, P < 0·001). After removing data from static cycling, which the IDEEA was unable to identify as an activity, both the IDEEA(est) and IDEEA(meas) methods overestimated EE compared to the calorimeter (9·9 MJ, P < 0·001; 9·1 MJ, P < 0·05 and 8·6 MJ, respectively). Similarly, the IDEEA system overestimated EE compared to DLW over 14 d; 12·7 MJ/d (P < 0·01), 11·5 MJ/d (P < 0·01) and 9·5 MJ/d for the IDEEA(est), IDEEA(meas) and DLW, respectively. The IDEEA system overestimated EE both in the controlled laboratory and free-living environments. Using measured EE values for RMR, sitting and standing reduced, but did not eliminate, the error in estimated EE.