Johnstone, A.M., Lobley, G.E., Horgan, G.W., Bremner, D.M., Fyfe, C., Morrice, P.C. and Duthie, G.G.
British Journal of Nutrition 106(2), 282-291.
Weight loss, antioxidant status, metabolic profile, cardiovascular disease, high-protein diet
||Purpose: There are concerns that a low-carbohydrate (LC) weight loss (WL) diet has a negative impact on antioxidant status and biomarkers of cardiovascular and metabolic health.
Methods: Sixteen obese men participated in a randomised, cross-over design diet trial, with food provided daily, at ~8.3 MJ/d (~70% energy requirements). They were provided two high protein diets (30% of energy), each for a 4-week period, involving a low-carbohydrate (LC, 4% carbohydrate) and moderate carbohydrate (MC, 35% carbohydrate). Body weight was measured daily and weekly blood samples collected.
Results: On average, ANOVA confirmed that subjects lost 6.75 and 4.32 kg of weight on the LC and MC diets, respectively (p<0.001, SED 0.350). The LC and MC diets were associated with a small lowering of plasma concentrations of retinol, vitamins E (-tocopherol) and -cryptoxanthin (p<0.005). However, such concentrations were not indicative of an overt deficiency. Surprisingly, plasma vitamin C concentrations increased on consumption of the LC diet (p<0.05). Plasma markers of insulin resistance (p<0.001), lipaemia and endothelial inflammatory response (p<0.05, TNF-. and IL10), improved similarly on both diets. There was no change in other cardiovascular markers with WL.
Conclusions: The current data suggests that a LC WL diet does not impair plasma indices of cardio-metabolic health, at least within four weeks, in otherwise healthy obese subjects. In general, improvements in metabolic health were similar between the LC and MC diets. However, antioxidant supplements may be warranted if LC WL diets are consumed for a prolonged period.