Plain language summary
Obesity is the leading cause of cardiovascular disease, diabetes, hypertension, hyperlipidaemia, and some forms of cancer. 38% of people worldwide are overweight, and 20% are obese. To combat obesity and associated comorbidities, calorie restriction (CR) is found to be a cost-effective non-pharmacological intervention. Intermittent energy restriction (IER) and continuous energy restriction (CER) are two forms of CR characterised by notable calorie restriction and normal energy intake phases. Forms of IER included in this research are the 5:2 diet, alternate-day fasting (ADF), and time-restricted feeding (TRF). For weight loss, CER limits calorie intake by 15-40%. A total of eleven randomised controlled studies were included in this systematic review and meta-analysis to compare the effectiveness of IER protocols with CER in reducing weight, BMI and waist circumferences in overweight or obese individuals. Improvements in anthropometric parameters were not different between IER and CER. A long-term robust study is necessary to evaluate the effects of IER and CER on improving anthropometric and metabolic parameters due to the limitations and heterogeneity of current research evidence. Nevertheless, healthcare professionals can use the results of this study to understand the role of IER and CER in weight loss and their clinical relevance for improving overall health and lifespan.
Abstract
There is considerable heterogeneity across the evidence regarding the effects of intermittent energy restriction and continuous energy restriction among adults with overweight or obesity which presents difficulties for healthcare decision-makers and individuals. This overview of systematic reviews aimed to evaluate and synthesize the existing evidence regarding the comparison of the two interventions. We conducted a search strategy in eight databases from the databases' inception to December 2021. The quality of 12 systematic reviews was assessed with A Measurement Tool to Assess Systematic Reviews 2 (AMSTAR 2) and the Grading of Recommendations Assessment, Development and Evaluation (GRADE). One review was rated as high quality, 1 as moderate, 4 as low, and 6 as critically low. A meta-analysis of the original studies was conducted for comparison of primary intermittent energy restriction protocols with continuous energy restriction. Intermittent energy restriction did not seem to be more effective in weight loss compared with continuous energy restriction. The advantages of intermittent energy restriction in reducing BMI and waist circumference and improvement of body composition were not determined due to insufficient evidence. The evidence quality of systematic reviews and original trials remains to be improved in future studies.
Methodological quality
Jadad score
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