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Background and aims: Weight loss by diet intervention has shown conflicting results on postprandial levels of glucagon-like peptide 1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP). We therefore investigated a Paleolithic diet (PD) and a prudent control diet according to the Nordic nutrition recommendations (CD) and aimed to compare the effect of the two diets on postprandial levels of GLP-1 and GIP.

Materials and methods: Seventy healthy, obese, postmenopausal women were randomized to either the PD or the CD. In the PD group participants were advised to eat vegetables, fruit, lean meat, fish, nuts and eggs. Cereals, dairy products, added sugar and salt were excluded. With the CD participants were advised to increase their intake of whole grain, fruit, vegetables and fish. Dairy products and meat were supposed to be low fat. Both diets were without calorie restriction. Plasma levels of GLP-1 and GIP were measured after ingestion of 75 g glucose at baseline and after 6 and 24 months of diet intervention. The incremental area under the curve (iAUC) of GLP-1 and GIP was calculated during 120 min after glucose intake.

Results: The PD group showed a more pronounced weight reduction after 6 months (9.2 ± 4.2 kg (mean±SD)) and 24 months (8.1 ± 5.6 kg) compared to the CD group (4.7 ± 4.2 kg at 6 months and 4.9 ± 4.8 kg at 24 months; P<0.001 and P<0.05 for the difference between groups at 6 months and 24 months). For the PD group the iAUC of GLP-1 increased by 34 % after 6 months and by 45 % after 24 months compared to baseline. For the CD group the iAUC of GLP-1 increased by 11 % after 6 months and by 59 % after 24 months. For the PD group the iAUC of GIP increased by 23 % after 6 months compared to baseline but decreased by 3 % in the CD group (P<0.05 for the difference between groups).

Conclusion: Postprandial levels of GLP-1 increased through dietinduced weight loss by the Paleolithic diet and the control diet. The postprandial GIP response increased through weight loss by the Paleolithic diet but not by the control diet.