Abdominal obesity is associated with elevated postprandial triglycerides (TG), an independent risk factor for cardiovascular diseases. Previous studies show that whey protein (WP) and dietary fiber may separately reduce postprandial TG. However, few studies have investigated the long-term effects of WP and dietary fiber on postprandial TG. We aimed to investigate the separate and combined long-term effects of WP and dietary fiber from wheat bran on postprandial TG and markers of lipid metabolism in subjects with abdominal obesity. We conducted a 12-week, double-blind, randomized, controlled, parallel intervention study. In a 2 × 2 factorial design, 73 adults were randomized to receive 60 g/day of either WP hydrolysate or maltodextrin (MD) combined with high-fiber wheat bran products (HiFi; 30 g dietary fiber/day) or low-fiber refined wheat products (LoFi; 10 g dietary fiber/day). A high-fat meal test was conducted before and after the intervention. Sixty-five subjects were included in the final analyses. There were no differences between intervention groups in postprandial TG assessed as incremental area under the curve (iAUC). WP-LoFi had reduced postprandial TG assessed as total area under the curve (tAUC) and reduced fasting TG compared with all other groups, and reduced fasting apolipoprotein B-48 compared with MD-LoFi. There were no changes in lipoprotein lipase activity. Total cholesterol and apolipoprotein B-100 were reduced after WP intake compared with MD. Total cholesterol was increased after HiFi intake compared with LoFi. In conclusion, intake of WP in combination with low-fiber cereal products for 12 weeks had beneficial effects on postprandial TG tAUC and fasting TG, but not on postprandial TG iAUC in subjects with abdominal obesity. Combining WP with high-fiber wheat bran products did not improve lipid profile.

Overnight fasting of varying length is common practice when studying glucose and lipid metabolism in rats. However, prolonged fasting may influence insulin sensitivity, and it is unknown to which extent different fasting durations affect postprandial metabolism in rats. The purpose of this study was to investigate the effect of different fasting durations (6-, 12-, or 18-h) on fat tolerance and glucose tolerance in male Sprague Dawley rats. We also aimed to examine the effect of two test fats with different fatty acid composition on postprandial triglycerides. We conducted a fat tolerance test, where butterfat or rapeseed oil was administered in a crossover design (experiment 1), and an oral glucose tolerance test (experiment 2). Regarding the fat tolerance test, we found no effects of fasting duration on triglycerides or free fatty acids, whereas the 18-h fast resulted in reduced glucose and insulin area under the curves. We did not find differential effects of butterfat and rapeseed oil on the outcomes. We found decreased fasting insulin and homeostasis model assessment of insulin resistance (HOMA-IR), and increased beta-hydroxybutyric acid concentrations after 18-h fast compared with shorter fasting durations. Regarding the oral glucose tolerance test, both 12-h and 18-h fast resulted in greater peak insulin concentrations than 6-h fast, and peak glucose concentrations were higher after 18-h than 12-h fast. We found no effects of fasting on the insulin sensitivity index. In conclusion, extending the fasting duration had an impact on glucose metabolism in rats, but did not appear to influence fat tolerance.

BACKGROUND : Abdominal obesity is characterized by low-grade inflammation and plays a central role in the development of type 2 diabetes and cardiovascular diseases. Dietary factors can influence low-grade inflammation and affect adipose tissue function. AIM : To investigate the separate and combined effects of whey protein and cereal fiber on inflammatory markers and adipose tissue gene expression in abdominal obesity. METHODS : We performed a 12-week, double-blind, randomized controlled dietary intervention in 65 adults with abdominal obesity. The participants were randomized to 4 groups using a 2 × 2 factorial design; they received either 60 g/day of whey protein or maltodextrin in combination with high-fiber wheat bran products (30 g fiber/day) or low-fiber refined wheat products (10 g fiber/day). Plasma concentrations of tumor necrosis factor α (TNF-α), high-sensitivity C-reactive protein (hs-CRP), monocyte chemoattractant protein-1 (MCP-1), interleukin 1 receptor antagonist (IL-1Ra), and adiponectin were measured before and after intervention. Changes in gene expression related to inflammation, insulin signaling, and lipid metabolism were measured in abdominal subcutaneous adipose tissue. RESULTS : After intervention, TNF-α was reduced for both high-fiber groups compared with baseline, but did not significantly differ from the low-fiber groups. There were no differences in fasting or postprandial inflammatory markers between the groups. The relative gene expression of ribosomal protein S6 kinase B1 ( S6K1 ) was increased after whey protein compared with maltodextrin consumption. CONCLUSION : Intake of whey protein in combination with high cereal fiber content did not differentially affect low-grade inflammation or adipose tissue gene expression compared with maltodextrin and low fiber content in individuals with abdominal obesity.