Weight loss achieved using an energy restriction diet with normal or higher dietary protein decreased the number of CD14++CD16+ proinflammatory monocytes and plasma lipids and lipoproteins in middle-aged, overweight, and obese adults.

Monocytes are involved in immune responses, and specific monocyte subpopulations (MS) that express intermediate to high levels of CD16 are associated with obesity and cardiovascular events. Consuming high protein (HP) when dieting improves body composition and cardiometabolic health outcomes, but whether HP affects MS during weight loss remains unknown. We assessed the effect of HP on energy restriction (ER)-induced changes in MS in overweight and obese adults. The relations between MS and plasma lipids and lipoproteins were also examined. We hypothesized that, independent of protein intake, ER-induced weight loss would decrease the numbers of MS and that MS and plasma lipids and lipoproteins would be related. Thirty-two adults (age 52 ± 1 years, body mass index 31.3 ± 0.5 kg/m2, means ± S.E.) consumed either a normal protein (n=18) or HP (n=14) (0.8 vs 1.5 g•kg-1•d-1 protein) ER diet (750-kcal/d [3138-kJ/d] deficit) for 16 weeks. The HP diet included 0.7 g•kg-1•d-1 of milk protein isolate. Fasting plasma lipids, lipoproteins, and the numbers of MS were analyzed. Over time, independent of protein intake, CD14++CD16+ cell number decreased, whereas CD14dimCD16++, CD14+CD16+, and CD14+CD16- cell numbers remained unchanged. CD14dimCD16++ cell number was negatively associated with total cholesterol (TC) and triglyceride, while CD14++CD16+ cell number was positively associated with TC, low-density lipoprotein cholesterol (LDL), TC to high-density lipoprotein cholesterol (HDL) ratio, and LDL to HDL ratio. Weight loss achieved while consuming an ER diet with either normal or high protein may improve immunity by partially decreasing proinflammatory monocytes. Associations between MS and plasma lipids and lipoproteins are confirmed in overweight and obese adults.