A critical review of low‐carbohydrate diets in people with Type 2 diabetes

Abstract

Aims The efficacy of low-carbohydrate diets (LCD) in people with Type 2 diabetes has divided the nutrition community. This review seeks to re-examine the available data to clarify understanding.Methods A comprehensive search of databases was used to identify meta-analyses of LCD in Type 2 diabetes. To improve the quality of the studies analysed, the following inclusion criteria were applied: randomized control trials ≥ 4 weeks in people aged > 18 years with Type 2 diabetes; a carbohydrate intake ≤ 45% of total energy intake per day; and a dietary intake assessment at the end of the study. The resulting studies were subjected to a thematic analysis.Results Nine meta-analyses were identified containing 153 studies. Twelve studies met our amended inclusion criteria. There were no significant differences in metabolic markers, including glycaemic control, between the two diets, although weight loss with a LCD was greater in one study. Carbohydrate intake at 1 year in very LCD (< 50 g of carbohydrates) ranged from 132 to 162 g. In some studies, the difference between diets was as little as 8 g/day of carbohydrates. ConclusionTotal energy intake remains the dietary predictor of body weight. A LCD appears no different from a highcarbohydrate diet in terms of metabolic markers and glycaemic control. Very LCDs may not be sustainable over a medium to longer term as carbohydrate intake in diets within studies often converged toward a more moderate level. The variable quality of studies included in earlier meta-analyses likely explains the previous inconsistent findings between meta-analyses.Diabet. Med. 33: 148-157 (2016)

Systematic review and meta-analysis of dietary carbohydrate restriction in patients with type 2 diabetes

“…The excess reduction in HbA1c was correlated with the degree of carbohydrate restriction, a finding not reported earlier. A recent review of the literature26 did not perform meta-analysis of the available HbA1c data due to a large heterogeneity in the carbohydrate intake in the intervention groups, and other meta-analyses have either shown a numerically greater reduction in HbA1c,6 7 or no effect in type 2 diabetes 9…”

“…Conclusions on the efficacy of LCD compared with HCD from recent reviews are thus conflicting with regard to glycemic control and weight loss 4–8. A very recent critical review based on predefined criteria9 found no evidence of any superiority of LCD compared with HCD.…”

4. Lifestyle Management:Standards of Medical Care in Diabetes—2018

“…Part of the confusion is due to the wide range of definitions for a low-carbohydrate diet (73,74). While benefits to low-carbohydrate diets have been described, improvements tend to be in the short term and, over time, these effects are not maintained (74)(75)(76)(77). While some studies have shown modest benefits of very low-carbohydrate or ketogenic diets (less than 50-g carbohydrate per day) (78,79), this approach may only be appropriate for short-term implementation (up to 3-4 months) if desired by the patient, as there is little longterm research citing benefits or harm.…”

Regulation of metabolic health and aging by nutrient-sensitive signaling pathways

“…While carbohydrate restriction initially lowered weight and fat mass in obese humans, over time this effect diminished, and weight benefits were not maintained (Hashimoto et al, 2016). Moreover, a recent meta-analysis of randomized control trials for low carbohydrate diets in subjects with type 2 diabetes suggests that a low carbohydrate diet does not improve glycemic control or other metabolic outcomes (van Wyk et al, 2016). …”