Fish Oil and Weight loss version 1
Research type
Research Study
Full title
Influence of dietary omega-3 fatty acid content on body composition changes during weight loss in resistance trained young men
IRAS ID
214516
Contact name
Iain Gallagher
Contact email
Sponsor organisation
University of Stirling
Duration of Study in the UK
2 years, 1 months, 1 days
Research summary
Research Summary
Weight loss, by means of low energy dieting, is an important consideration for many athletes. Athletes desire weight loss for several reasons, including improving power-to-mass ratio and the necessity to make weight categories. However, total weight lost includes both fat mass and muscle mass. If significant muscle mass is lost, athlete performance may be compromised. Alternatively, if muscle mass is preserved, athlete performance may be improved. It has previously been demonstrated that loss of muscle mass is reduced while achieving similar loss of fat mass in resistance-trained males undertaking a high protein, low energy diet (~Energy% - 35 protein) compared with a low energy diet of conventional macronutrient composition (~Energy% - 15 protein, 50 CHO, 35 fat). The composition of dietary fat also may be an important component of a low energy diet. The inclusion of omega-3 fatty acids (n3-PUFA) into a low energy diet has been reported to promote weight loss in overweight/obese men and women. Recent data has also suggested dietary n3-PUFA preserve muscle mass during catabolic situations (when muscle is broken down) such as immobilisation and weight loss. In this study, 30 young males who have been resistance training for at least 6 months will be recruited from the Stirling area. Participants will be allocated to one of two groups, which will be matched for average baseline plasma n-3 PUFA concentration; 1) low energy (60% of habitual energy intake), supplemented with n-3 PUFA; 2) low energy (60% of habitual energy intake), supplemented with a placebo. Participants will be supplemented with n-3 PUFA for 6 weeks. The first 4 weeks, participants will consume their habitual diet. In the final 2 weeks, energy restriction will occur. Changes in body composition, sporting performance, muscle signaling and mRNA expression will be compared between groups at baseline, before and after the weight loss period.
Summary of Results
We investigated whether omega-3 fish oils could spare muscle mass during a period of weight loss in healthy trained male athletes. Normally when you lose weight, you will lose both fat and muscle mass. However, loss of muscle can have negative impacts on body function, including exercise performance. Omega-3 fish oils have been shown in other studies to improve muscle function and health. To investigate whether omega-3 fish oils could reduce the amount of muscle mass lost during a period of weight loss, we supplemented 10 healthy active men with fish oil and 10 with placebo supplements for a period of 6 weeks, in a randomised way. The supplements contained 4 grams per day of omega-3 fish oil. During the first 4 weeks of the study, participants consumed their normal diet. We then lowered the amount of calories they consumed for the last 2 weeks to 60% of their normal diet, so that they would lose about 3kg of total body weight. They continued to do their normal exercise during this period, and we monitored their energy intake (diet) and expenditure (physical activity). Participants ended up losing an average of 3.2kg total weight, so the weight loss period was successful. However, there was no difference between the two supplemental groups (FO & PLA) in terms of how much muscle mass was lost, as both groups lost about 1.1kg of lean mass. We used dual energy x-ray absorptiometry (DEXA) scans to measure changes in body composition in our participants, which is a reliable way of measuring body composition. We also measured changes in muscle function, through performance of muscle strength and endurance tests. There was also no difference between FO and PLA groups in how these were performed. Further, we measured changes in energy metabolism (the amount of energy you use to keep yourself alive), and also did not find any difference between groups. At the start and end of the weight loss period (weeks 4 and 6), we took small bits of muscle tissue from people’s legs, via muscle biopsy. These samples were analysed for activity of specific proteins involved in the building of new muscle proteins, and expression of genes related to muscle development. We did not find evidence that omega-3 fish oils had any impact on these proteins or genes. As we did not find any effect of omega-3 fish oils on changes in body composition during weight loss, they should not be recommended for this purpose.
REC name
West of Scotland REC 4
REC reference
16/WS/0248
Date of REC Opinion
23 Jan 2017
REC opinion
Further Information Favourable Opinion