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In a fed and orally stimulated state, whether the addition of monosodium glutamate (MSG) (alone or in combination with inosine monophosphate-5 (IMP-5)) to a high-protein (HP) meal leads to early satiety and a difference in energy intake at a second course was investigated. Ten men and twelve women consumed, in random order, a first-course meal consisting of: (1) water (control); (2) a HP meal with 0·6 % MSG and 0·25 % IMP-5; (3) a HP meal with no additives; (4) a HP meal with MSG only; (5) a sham-fed meal 2 (oral-stimulation). Appetite perceptions, plasma concentrations of glucagon-like peptide 1 (GLP-1), glucose and insulin, and energy intake at a buffet (i.e. a second course) were measured before and after each condition. Changes in appetite, and in GLP-1, glucose and insulin, were similar for the three fed HP conditions and all were greater (post hoc all P sem 0·3) MJ) as compared with the HP+MSG-only (2·24 (sem 0·28) MJ) condition (P = 0·08), or for the HP+MSG+IMP compared with the HP no-additives condition (1·60 (sem 0·29) MJ) (P = 0·21). Following the HP+MSG-only condition, 0·64 (sem 0·20) MJ more energy was consumed compared with the HP no-additives condition (P = 0·005). We conclude that the addition of MSG to a HP meal does not influence perceptions of satiety and it may increase energy intake at a second course. Cephalic responses after the sham condition were of similar magnitude to the control and therefore just tasting food is not enough to influence appetite and energy intake.

The aim of the present study was to determine individuals' taste threshold for monosodium glutamate (MSG) alone and in combination with inosine 5′-monophosphate (IMP-5) and to examine if this threshold was related to an increase in sensory properties (including pleasantness of taste) and/or to one's preference for dietary protein over carbohydrate and fat. Using the triangle tasting method, the taste threshold was determined for thirty-six women and twenty-four men. Thresholds varied from zero to infinite as determined using a clear soup with added MSG in the concentration range of 0·1 to 0·8 % (w/w) MSG. Subjects rated fourteen sensory properties of the soup and also their ‘liking’, ‘eating frequency’ and ‘preference’ of twenty-two common high-protein, high-carbohydrate and high-fat food items. The taste threshold (and therefore sensitivity) of MSG was lowered from 0·33 (sem 0·24) to 0·26 (sem 0·22) % MSG when 0·25 % (w/w) IMP-5 was added. None of the sensory properties assessed was associated with the taste threshold of MSG ± 0·25 % IMP-5 in the overall study population. However, the taste descriptor ‘meatiness’ was associated with the threshold data for individuals who could taste concentrations of ≤ 0·4 % MSG. ‘Liking’ and ‘preference’ scores for protein were found to be related to the threshold of MSG ± 0·25 % IMP-5. From this study population we conclude that the taste threshold of MSG in combination with IMP-5 does appear to predict one's ‘liking’ of as well as ‘preference’ for high-protein foods.

The aim of this study was to determine after 52 weeks whether advice to follow a lower carbohydrate diet, either high in monounsaturated fat or low fat, high in protein had differential effects in a free-living community setting. Following weight loss on either a high monounsaturated fat, standard protein (HMF; 50 % fat, 20 % protein (67 g/d), 30 % carbohydrate) or a high protein, moderate fat (HP) (40 % protein (136 g/d), 30 % fat, 30 % carbohydrate) energy-restricted diet (6000 kJ/d) subjects were asked to maintain the same dietary pattern without intensive dietary counselling for the following 36 weeks. Overall weight loss was 6·2 (sd 7·3) kg (P sd 8·1) kg, HMF v. 4·8 (sd 6·6) kg, HP). In a multivariate regression model predictors of weight loss at the end of the study were sex, age and reported percentage energy from protein (R2 0·22, P P sd 4·6) to 10·2 (sd 5·2) mIU/l, but fasting plasma glucose was not reduced. Neither total cholesterol nor LDL-cholesterol were different but HDL was higher, 1·19 (sd 0·26) v. 1·04 (sd 0·29) (P sd 1·23) v. 2·22 (sd 1·15) mmol/l (P sd 2·84) to 2·43 (sd 2·29) mg/l, P