Preferential reduction in adipose tissue α-linolenic acid (18∶3ω3) during very low calorie dieting despite supplementation with 18∶3ω3

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Abstract
We have previously reported that the relative content of 18∶3ω3 in adipose triglyceride (TG) of women was reduced following major weight loss while on a very low calorie diet (VLCD). In an attempt to prevent this loss of 18∶3ω3 reserves, we have tested two VLCD supplemented with varying amounts of 18∶3ω3. The formula (FORM) and food VLCD (2.1–3.0 MJ or 500–700 kcal/d) contained 20 g/d of fat and provided the recommended dietary allowance for minerals and vitamins. FORM subjects (Group 1) were 5 women [initial body mass index (BMI) of 36.8, 168% ideal body weight (IBW) who received 20 g/d of canola oil (1.6 g 18∶3ω3). Their mean weight loss was 23.9 kg in a 4–5 mon period. Food VLCD subjects (Group 2) were 6 women (BMI 33.9, 155% IBW) supplemented with 2 g/d of linseed oil (1.1 g 18∶3ω3). Their mean weight loss was 17.4 kg in a 2–3 mon period. Needle biopsies of adipose tissue were obtained from Group 1 before, at midpoint and after weight loss; and from Group 2 before and after weight loss. The adipose TG and serum (Group 1) were separated and their fatty acid composition determined by thin-layer and gas chromatography. In Group 1, adipose 18∶3ω3 fell from 0.65 to 0.59 wt%, then to 0.52 wt% during weight loss. In Group 2, it fell from 0.77 to 0.64 wt%. The fall in adipose 18∶3ω3 with weight loss was significant atP=0.01 (Group 1) andP<0.01 (Group 2). There were no differences between responses to the 1.1 g/d or 1.6 g/d 18∶3ω3 supplements. The relative content of 18∶3ω3 in serum free fatty acids from Group 1 was reduced after major weight loss. Thus, in both groups the ω3 supplementation did not help to maintain adipose tissue 18∶3ω3 during rapid weight loss, and its decrement may affect circulating lipid pools. As adipose 18∶2ω6 did not change with weight loss, this reduction in the ratio of ω6 precursor to ω3 precursor could eventually alter the balance of their products as well.