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Bays · Postgraduate medicine 2009 · randomized, double-blind, placebo-controlled trial with open-label extension · n=167

The effect of prescription omega-3 fatty acids on body weight after 8 to 16 weeks of treatment for very high triglyceride levels.

Cited 23 times in the scientific literature.

Level 2 - randomized trial

Individual randomized controlled trial with an open-label extension

PubMed 19820283 · doi:10.3810/pgm.2009.09.2061 · record verified 2026-08-26

What was done

This study evaluated body weight and waist circumference changes in 167 overweight or obese adults (BMI 25–43 kg/m², aged 18–79 years) with severe hypertriglyceridemia (triglycerides 500 to <1300 mg/dL). Participants were evaluated during an 8-week randomized, double-blind, parallel-group trial comparing prescription omega-3-acid ethyl esters (P-OM3, 4 g/day contributing ~44 kcal/day) plus fenofibrate (130 mg/day; n = 84) versus corn oil placebo (4 g/day) plus fenofibrate (130 mg/day; n = 83), followed by an 8-week open-label extension (n = 117) where all participants received P-OM3 plus fenofibrate.

What was found

During the 8-week double-blind phase, median (min, max) change in body weight did not significantly differ between P-OM3 and placebo (0 [-4.6, +4.2] kg vs 0 [-3.6, +5.5] kg; P = 0.088), nor did waist circumference (+0.1 [-12.1, +17.5] cm vs +0.5 [-9.9, +12.2] cm; P = 0.162). In the 8-week open-label extension, non-switchers and switchers showed no significant differences in weight change (+0.2 [-3.2, +5.6] kg vs +0.1 [-6.9, +7.9] kg; P = 0.982) or waist circumference change (+0.1 [-9.8, +41.8] cm vs +0.2 [-12.0, +7.0] cm; P = 0.685).

Why it matters

The modest daily caloric contribution of high-dose prescription omega-3 fatty acids (4 g/day) does not cause weight gain or increase central adiposity when coadministered with fenofibrate in dyslipidemic patients over 8 to 16 weeks.

Limits

The study duration was relatively short (up to 16 weeks) with modest sample size (167 randomized, 117 in the open-label extension). All participants received concurrent fenofibrate, confounding isolated omega-3 effects. The comparator in the randomized phase was an isocaloric corn oil placebo rather than a non-caloric control, dietary intake was not reported, and the second phase was unblinded.

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