The Meal Frequency Project : The effect of meal frequency on body composition during 12-weeks of strength training

Abstract Background: Human trials on the effect of meal frequency on body composition are scarce. Short-term studies show increased rate of protein synthesis immediately after intake of amino acids (Rennie 2002), and frequent meals are shown to aid in the preservation of lean body mass when dieting (Iwao 1996). Consequently it could be hypothesised that in response to strength training interventions, more frequent meals will give larger muscle mass accumulation and lower fat mass than fewer meals. Objective: The purpose of this study was to compare the effects of dividing the daily food intake in 3 versus 6 meals per day on changes in body composition in young men and women performing strength training over 12 weeks. Design: Men (n=33) and women (n=15) aged 21 to 35 with at least one year of previous strength training experience were matched according to strength and gender and then randomly assigned to either a 6M group or a 3M group. The prescribed total dietary intake was equal between the groups and was calculated to give a positive energy balance of approximately 1200 KJ/day, a protein intake of 1.5-1.7 g/kg/day and a carbohydrate intake of 5-7 g/kg/day (Table 1). During the training period the dietary intake was controlled by repeated 24-hours recalls. All participants performed the same periodized 2-split strength-training programme, training four times per week, giving each muscle group one heavy session and one light session per week. In the heavy sessions, training intensity varied between 10 and 3 RM sets, and 3-6 sets were performed in each exercise. Project leaders, giving every participant the necessary assistance, supervised all heavy sessions. Determination of body composition was performed with DEXA at the beginning of, in the middle of and immediately after the trial. Results: A total of 16 men and 11 women completed the project. The 3M group had a strong tendency towards greater gain in LBM than the 6M group after twelve weeks of strength training, 1.71% {-0.18, 3.59}, p=0,075. After linear regression analysis the difference was significant when adjusted for gender and energy intake (p=0.045), when adjusted for gender and protein intake (p=0.027), and when adjusted for gender, protein intake, carbohydrate intake and fat intake (p=0.011). There were no significant differences in change in fat mass between the groups, but a tendency towards a greater gain in the 3M group, 7.33% {-5.23, 19.90}, p=0.241. The 3M group had a 2.87% {0.62, 5.12} larger weight gain than the 6M group, p=0.014. Both groups had significant increases in strength in all test exercises. The 3M group had a larger strength gain in bench press, 10.85% {3.38, 18.32}, p=0.006 and triceps pushdown, 12.81%, {3.14, 22.47}, p=0.011 and a larger strength gain for the upper body, 8.37% {1.61, 15.13}, p=0.017 and total body, 6.28 {0.46, 12.09}, p=0.035 than the 6M group. The participants had a 2.31% {0.83, 3.79}, gain in bone mineral density of the spine during the twelve weeks of strength training, p=0.003, but there were no differences between the groups. Conclusion: In this study, three meals per day resulted in larger muscle- and strength gain from strength training when in positive energy balance than six meals per day over a period of twelve weeks. The reason why we draw opposite conclusions from short-term studies needs further investigation. More long-term studies are needed to determine the optimal meal frequency for ultimate gain in LBM from strength training, and larger groups may be needed to determine an effect of meal frequency on fat mass. The changes in fat mass had large variations within and between the groups, making it difficult to draw any conclusions. Key words: Meal frequency, strength training, lean body mass, fat mass, bone mineral density, DEXA