Abstract
Low-carbohydrate diets (LCDs) often differ in their diet composition, which may lead to conflicting results between randomized controlled trials. Therefore, we aimed to compare the effects of different degrees of carbohydrate (CHO) restriction on cardiometabolic risk markers in humans. The experimental LCDs of 37 human trials were classified as (1) moderate-low CHO diets (<45–40 E%, n = 13), (2) low CHO diets (<40–30 E%, n = 16), and (3) very-low CHO diets (<30–3 E%; n = 8). Summary estimates of weighted mean differences (WMDs) in selected risk markers were calculated using random-effect meta-analyses. Differences between the LCD groups were assessed with univariate meta-regression analyses. Overall, the LCDs resulted in significant weight loss, reduced diastolic blood pressure BP, and increased total cholesterol and high-density lipoprotein cholesterol (HDL-C), without significant differences between the three LCD groups. Higher low-density lipoprotein cholesterol (LDL-C) concentrations were found with the very-low CHO diets compared to the moderate-low CHO diets. Decreases in triacylglycerol (TAG) concentrations were more pronounced with the low and very-low CHO diets, compared to the moderate-low CHO diets. Substitution of CHO by mainly saturated fatty acids (SFAs) increased total cholesterol, LDL-C, and HDL-C concentrations. Except for LDL-C and TAGs, effects were not related to the degree of CHO restriction. Potential effects of nutrient exchanges should be considered when following LCDs.
Highlights
Low-carbohydrate diets (LCDs) have been proposed in the management of obesity, diabetes, and cardiovascular diseases (CVD) [1,2,3]
Randomized controlled trials (RCTs) have shown conflicting results on the effects of LCDs on weight loss, glycemic control, and serum lipid profiles, while positive effects have mainly been observed in short-term studies [4]
Authority concluded that scientific evidence is not sufficient to advocate either low or high carbohydrate (CHO) diets and recommends a range for CHO-intake between 45% to 60% of total energy (E%), including a daily fiber intake of at least 25 grams [5]
Summary
Low-carbohydrate diets (LCDs) have been proposed in the management of obesity, diabetes, and cardiovascular diseases (CVD) [1,2,3]. Authority concluded that scientific evidence is not sufficient to advocate either low or high carbohydrate (CHO) diets and recommends a range for CHO-intake between 45% to 60% of total energy (E%), including a daily fiber intake of at least 25 grams [5]. In the human intervention trials performed so far, intakes of CHO differed widely between studies, which implies varying amounts of fats and proteins. It is well-known that different degrees of Nutrients 2020, 12, 991; doi:10.3390/nu12040991 www.mdpi.com/journal/nutrients
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