Polyunsaturated fatty acids as modulators of fat mass and lean mass in human body composition regulation and cardiometabolic health.

Key Points

The purpose of this paper is three‐fold: (i) to bring forward the emerging evidence, from both observational and intervention (RCT) studies, of a role for PUFA—in particular, the essential fatty acids—in the long‐term regulation of body weight and body composition, (ii) to examine their impact on cardiometabolic health, and (iii) to discuss current notions about the mechanisms by which PUFAs modulate fat mass and lean mass through altered control of energy intake, thermogenesis, and lean–fat partitioning.

The reviewed studies in healthy men and women indicate that dietary unsaturated fatty acids enter oxidation pathways to a greater extent than dietary SFA, although it is not clear whether among the unsaturated fatty acids, there are significant differences in the postprandial oxidation between PUFA and MUFA, or among the different dietary PUFAs.

This analysis included data from 121,335 men and women (free of diabetes, cardiovascular disease, cancer, or obesity) and was performed by applying multivariate models adjusted for potential confounders (that included age, baseline BMI, and change in percentage energy from protein, intake of cereal fiber, fruits, and vegetables, alcohol use, and other lifestyle covariates). The results indicated that increasing consumption of n‐6 and n‐3 PUFA, as well as plant‐based MUFA, at the expense of carbohydrate was associated with less weight gain, whereas increasing intake of SFA, trans fat, and MUFA from animal sources was associated with greater weight gain. Further examination of PUFA types revealed that while the inverse association between n‐6 PUFA intake and weight gain was mainly driven by LA, the inverse association between n‐3 PUFA and weight gain was driven by n‐3 PUFA from both marine (EPA and DHA) and plant origin (ALA).

Based on both epidemiological (prospective) studies and clinical (RCT) evidence, it appears that ePUFA (LA and ALA) may have greater beneficial effects on long‐term weight homeostasis, and adiposity, as well as on glycemic control than marine‐derived PUFA. Furthermore, as discussed below, the two ePUFAs may influence human body composition by modulating not only body fat but also lean body mass. A closer examination of the literature reveals that plant‐based essential fatty acids (ePUFAs; LA and ALA) may be more effective than marine‐derived PUFAs (EPA and DHA) in modulating human body composition (and glucose homeostasis), at least in adults. While this notion requires more robust testing in long‐term RCT, much remains to be done in terms of gaining a better understanding of mechanisms by which ePUFAs modulate body fat and lean mass, whether centered around altered control of energy intake, thermogenesis, or lean–fat partitioning.

The ePUFA, which derive principally from vegetable oils, may represent a more affordable alternative for improving the lipid quality of the diet. However, dietary intake of ePUFA is suboptimal in many countries, particularly among lactating women, adolescents, and the elderly. This is compounded by a dramatic change in the composition of vegetable oils in certain countries over the past decade (reducing their LA content), the long‐term effects of which have yet to be revealed. Thus, given the benefits of ePUFA highlighted herein, which in some cases exceed those of the n‐3 long‐chain PUFAs, increasing ePUFA intake stands to have major implications for public health and clinical medicine, as much for the prevention of obesity as for the management of musculoskeletal and cardiometabolic health across the life cycle.