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.