Differences in Diet Induced Thermogenesis and Satiety with Different Protein Loads

Abstract

Background: Evidence supports the effect of protein to increase diet induced thermogenesis and satiety; promoting effective weight loss in the management of obesity [1,2]. However, there is limited evidence to indicate the optimum protein source that will elicit maximum effects on diet induced thermogenesis and satiety. This study aims to investigate the effect of isocaloric meals containing varying protein sources on diet induced thermogenesis and satiety in healthy individuals. Methods: The study applied a cross over design and recruited healthy individuals; both male and female via the University recruitment moderator email. Participants completed a screening questionnaire and those with food intolerances to the meals provided, claustrophobia or metabolic disturbances were excluded from the study. Participants attended two separate testing sessions and completed 24 hour diet histories pre and post testing sessions. Participants were required to fast and refrain from vigorous physical activity for 12-14 hours respectively prior to testing. On their initial visit; weight, height and BMI were recorded. Resting energy expenditure, using indirect calorimetry, and appetite parameters, using 10 mm visual analogue scales (VAS), were measured at each testing session. Participants were provided with a different meal at each session containing varying protein sources. Meal 1: Porridge and milk (Kcals 267, P 15.4g, CHO 31.5g, Fat 9.6g), Meal 2: Scrambled eggs (Kcals 266, P 16.6g, CHO 20g, Fat 13.9g). Post meal consumption energy expenditure was recorded until resting values were re-established. Diet induced thermogenesis (DIT) was calculated using an area under the curve (AUC) calculation and a paired two tailed t test was used in order to determine differences in appetite parameters as well as caloric intake and typical intake post meal consumption. A significance level of P ≤0.05 was applied. Ethical approval was granted from the Queen Margaret University Ethics Committee.  Results: 10 participants, male to female ratio of 1:9, aged 22-29 years and BMI range of 20-24Kg/M2 completed testing. Energy Expenditure (EE) was found to be significantly higher post consumption of Meal 1 (P= 0.001). From this, DIT was calculated. A greater DIT of 2691.5 AU was calculated for Meal 1, porridge and milk, in comparison to 796 AU for the scrambled egg, Meal 2.  Discussion: Meal 1 elicited significantly higher EE (P =0.001) and produced over 3 fold the levels of DIT to Meal 2. Meal 1 was significantly more satiating for ‘How much could you eat’ and ‘Desire to eat’. Evidence supports higher protein diets result in increased levels of EE and satiety in comparison to isocaloric diets consisting of lower protein quantities or higher quantities of alternative macronutrients, however, limited research exists on individual protein sources [2]. Limitations include: small cohort and differences in macronutrient quantities of meals.  Conclusions: This study demonstrated that different protein sources elicit varying degrees of diet induced thermogenesis and satiety in a group of healthy individuals, however, further research is needed to ascertain the optimum protein source to produce the most significant effects on DIT and satiety.