ReviewEfficacy of low carbohydrate diet for type 2 diabetes mellitus management: A systematic review and meta-analysis of randomized controlled trials
Introduction
Diabetes mellitus is the dominant cause of a range of complications and death worldwide. Approximately 422 million people are living with diabetes in 2014 [1]. Type 2 diabetes patients usually accompanied with overweight or obesity, and excessive body mass index (BMI) increases result in the risk of diabetes rises [2]. A traditional diet of energy-restriction, high-carbohydrate, low-fat and low-protein have been recommended for the weight loss of diabetes patients [3]. However, in recent years, studies demonstrate that dietary carbohydrates are a major factor in blood glucose control, and it can aggravate postprandial glucose responses [4], [5]. Therefore, the program of carbohydrate restriction was proposed to use to lose weight in many studies, and the efficacy of low carbohydrate diet (LCD) for diabetes management also has been widely discussed by researchers.
The LCD is a program which carbohydrate intake is less than 130 g/day or 26% of daily energy from carbohydrates [4]. Previous studies indicate that LCD can reduce blood glucose and body fat, improve insulin sensitivity, and decrease triglyceride and cholesterol levels among patients with diabetes [6], [7], [8], [9]. In a randomized controlled trial (RCT), intervention with LCD has been found to reduce weight, HbA1c, and the level of fasting insulin [10]. Moreover, based on the present researches, the American Diabetes Association (ADA) considers that LCD is similarly effective for weight loss compared with low-fat calorie-restricted diets [11].
But, over the past decades, the issue of carbohydrate restriction has still been a controversial problem, particularly in patients with type 2 diabetes. Although dietary carbohydrates increase postprandial blood glucose levels, total carbohydrate restriction will not return the blood glucose to the normal range [5]. According to the research by Davis et al., one year LCD intervention has a similar effect on weight loss and glycemic control compared with a low-fat diet [12]. Other several studies concern that low-carbohydrate high-fat diet may aggravate the lipid profile, cardiovascular risk factors of patients with diabetes [13]. Two cohort studies indicate that the LCD group based on animal source protein has a greater increase in all-cause mortality [14].
Thus, considering the potential efficacy of LCD in type 2 diabetes management, we conducted this systematic review and meta-analysis of RCTs to evaluate the overall effect of LCD on weight loss, blood glucose, and blood lipid concentrations in diabetic patients.
Section snippets
Literature search
We searched MEDLINE, EMBASE, and the Cochrane Library database from inception through January 2017. There were no publication time and language restriction. The relevant articles were identified using the following search items: (“low carbohydrate diet” OR “ketogenic diet” OR “Atkins diet”) AND (“diabetes” OR “diabetes mellitus”). In addition, we searched reference lists of included studies and other potentially relevant studies. We would request original information from the authors by e-mail
Results of the literature search
Fig. 1 shows the flow diagram of the study selection process. We initially identified 2322 potentially study in the literature search, of which 611 were duplicates articles. After title and abstract review, 1676 were excluded because the studies did not meet the inclusion criteria. Among the remaining studies, 6 were non-RCTs, 3 were systematic review and 2 trials did not report the relevant outcomes. The target population of 3 studies was not type 2 diabetes. Finally, full-text assessment of
Discussion
Our meta-analysis is the first one to evaluate the efficacy of LCD for type 2 diabetes management. Nine RCTs with 734 participants were included in our current research. The finding from this meta-analysis suggested that LCD intervention had a positive effect on HbA1c, TG, and HDL-c concentrations. There was no significant efficacy of LCD in improving TC and LDL-c concentrations. The result also indicated that LCD intervention reduced the body weight of patients, but it did not achieve
Conclusion
In conclusion, LCD intervention showed a beneficial effect on improving HbA1c level compared with the high or normal carbohydrate dietary, suggesting LCD might be effective for type 2 diabetes management. The result also suggested that LCD may be beneficial to cardiovascular risk factors, according to summaries of data of TG and HDL-c concentrations. But, there was no evidence to show that LCD was effective for reducing TC and LDL-c concentrations. Although no significant association was found
Conflicts of interest
None declared.
Funding source
This work was supported by the National Natural Science Foundation of China [Grant No. 81470498].
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The authors contribute equally to this paper.