12 January - 20 June 2016

A high poly-unsaturated diet may alter hormones associated with hunger and satiety

A small study, published in the journal Nutrition and sponsored by the California Walnut Commission, has suggested that consuming a high poly-unsaturated fat (PUFAs) diet may alter appetite hormones associated with hunger and satiety.

A small study, published in the journal Nutrition and sponsored by the California Walnut Commission, has suggested that consuming a high poly-unsaturated fat (PUFAs) diet may alter appetite hormones associated with hunger and satiety.

Cooper et al. report that previous studies have indicated that consuming dietary PUFAs can prevent disease, reduce food intake, increase energy expenditure and lower body weight amongst others.  Although they note however that “research on subjective and satiety response to long-term consumption of a PUFA-rich diet is lacking”. The hormone Ghrelin is thought to have appetite stimulating effects, and levels of the hormone in the blood are increased during fasting.  Another hormone peptide YY (PYY), secreted by the colon and small intestine in response to feeding, acts to reduce appetite.  

The study involved 26 healthy, sedentary adults aged 18 to 35 years. Before the start of the intervention the participants consumed a 3-day lead-in diet, that the authors’ state was representative of the average US diet (providing around 29%, 31% and 40% of energy at breakfast, lunch and dinner respectively).  Following the lead-in diet, Cooper et al. analysed the participants’ blood including fasting measurements and took various body measurements. The scientists also took blood samples at numerous intervals (up to 8 hours) after the participants had consumed two high fat meals at breakfast and lunch.

After the pre-diet visit the participants were splits into two groups and received either a PUFA rich diet (% energy from fatty acid – 21% PUFA, 5% SFA, 9% MUFA) or a control diet (% energy from fatty acid – 7% PUFA, 13% SFA, 15% MUFA) for seven days.  The control diet had the same macronutrient and fatty acid breakdown as the lead-in diet.   PUFAs were provided by foods such as walnuts, salmon, tuna, flax seed oil, grapeseed oil and canola oil.  The participants on the PUFA diet also consumed an additional 3g/d of combined eicosapentaenoic acid (EPA 2157 mg/day) and docosahexaenoic acid (DHA 843 mg/day).  After the 7 days, the participants underwent the same tests and measurements for the pre-diet visit. 

The scientists analysed fasting concentration of ghrelin, PYY, insulin and leptin from pre- to post-diet intervention and found that the PUFA rich diet led to a significant decrease in fasting ghrelin concentrations (a decrease in the range of 200 pg/ml compared to the pre PUFA rich diet) and a significant increase in fasting PYY concentrations (increase in the range of 30 pg/ml).  There were no changes in fasting insulin or leptin (a satiety hormone release by adipose tissue as well as small amount from the gastrointestinal tract), and no change in any fasting hormones for the control diet.  The scientists also found that “the postprandial response to the high fat meals showed a significant greater PYY response after the 7 day PUFA-rich diet”.  They state “these findings show that the PUFA rich diet elicited greater physiological satiety through greater ghrelin suppression and higher PYY levels in healthy weight adults.”  Using a subjective visual analogue scale (VAS) the researchers measured hunger, fullness and how much food the participants thought they could eat, although they found no changes in VAS in either treatment.  They state “the results of the study showed that consuming a PUFA-rich diet favourably alters some hunger and satiety hormone responses but does not significantly alter subjective rating of hunger or fullness.

RSSL's Lipids Laboratory, can determine the fatty acid profile of all dietary fats and oils including trans fats.  For more information please contact Customer Services on +44 (0) 118 918 4076 or email enquiries@rssl.com

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