Intermittent calorie restriction proves as effective as daily calorie cuts for type 2 diabetes

New clinical research suggests both continuous and intermittent calorie restriction improve metabolic health in type 2 diabetes, with adherence emerging as a key factor in real-world success.

Study: The effect of continuous or intermittent calorie-restricted diet on body composition and resting energy expenditure in patients with type 2 diabetes. Image Credit: Oleksandra Mykhailutsa / Shutterstock

In a recent article submitted to the journal Clinical Nutrition ESPEN, a group of researchers evaluated how a three-month continuous calorie-restricted (CCR) diet compared with an intermittent calorie-restricted (ICR) diet affects body composition and resting energy expenditure in adults with type 2 diabetes and overweight or obesity, based on a post-hoc analysis combining participants from two separate randomized trials rather than a direct head-to-head randomized comparison.

Background

More than 500 million people worldwide live with type 2 diabetes, and excess weight remains one of its most significant causes. Losing even a modest amount of weight can improve blood glucose levels, reduce medication requirements, and lower the risk of cardiovascular disease. Traditionally, CCR has been used; however, there is increasing interest in intermittent diets. Both methods can create a caloric deficit, leading to weight loss; however, the amount of fat-free mass, including muscle, determines the magnitude of the decrease in resting energy expenditure after weight loss and may impair long-term maintenance of a healthy weight.

Maintaining muscle during weight loss is vital in older adults with diabetes. Further research is needed to clarify which strategy better protects metabolic health, particularly because between-group comparisons in this study were exploratory and not powered for definitive conclusions, and because the intervention lasted only three months, limiting conclusions about long-term sustainability.

About the study

This post-hoc analysis included adults with type 2 diabetes and a body mass index above 27 kilograms per square meter who participated in two separate ongoing randomized controlled trials in the Netherlands, E-DIET and TIMED, from which intervention groups were pooled for analysis. Participants followed either a CCR diet or an ICR diet for three months.

The CCR group consumed approximately 750 kilocalories per day from meal replacements, with low-carbohydrate vegetables provided in addition to lean protein, low-energy drinks, and skim milk. The ICR group followed an early time-restricted eating pattern, consuming all calories between 8:00 AM and 6:00 PM, with a daily intake of 1300 kilocalories for women and 1500 kilocalories for men, alongside moderate carbohydrate restriction.

Fat mass, fat-free mass, and phase angle, a marker of cellular health and nutritional status rather than hydration alone, were measured using a multi-frequency bioelectrical impedance device to determine body composition. Resting energy expenditure was calculated using indirect calorimetry under controlled laboratory conditions. Glycemic control was evaluated using fasting glucose and glycated hemoglobin. Lipid profile, blood pressure, diabetes medication use (assessed using the Medication Effect Score), dietary intake, physical activity, and treatment satisfaction were also recorded. Statistical analyses examined within-group changes and exploratory comparisons between groups, adjusting for baseline differences such as diabetes duration and glycemic control.

Study results

In total, 67 participants were included in the analysis: 41 in the CCR group and 26 in the ICR group. The average age was approximately 60 years, and more than half were women. Body mass index values were similar between groups at baseline, but diabetes duration was longer in the CCR group, and other metabolic differences were present, limiting direct comparability.

After three months, both diets produced significant weight loss. On average, participants following the CCR diet lost 7.4 kg, whereas those following the ICR diet lost 6.8 kg. Both groups showed significant reductions in body mass index and waist circumference, suggesting reduced central adiposity rather than a direct reduction in abdominal fat.

Fat mass decreased significantly in both groups. The percentage of fat-free mass increased in both interventions, although absolute fat-free mass declined modestly in the ICR group, indicating that percentage increases do not necessarily reflect true muscle gain. Absolute fat-free mass was preserved in the CCR group and decreased modestly in the ICR group, representing approximately 20 percent of total weight loss, consistent with expected physiological adaptation. Muscle strength or sarcopenia was not directly assessed.

Resting energy expenditure decreased significantly only in the CCR group. This decrease may reflect adaptive thermogenesis rather than solely fat-free mass loss, as the body conserves energy during substantial caloric restriction. In practical terms, lower resting energy expenditure may make long-term weight maintenance more challenging.

Glycated hemoglobin improved significantly in the CCR group, while fasting glucose did not change significantly in either group. Both groups reduced diabetes medication use, as reflected by reductions in Medication Effect Score rather than by confirmed medication discontinuation. Total cholesterol and low-density lipoprotein cholesterol improved significantly in the CCR group, while high-density lipoprotein cholesterol increased in the ICR group. Triglycerides decreased in both groups. Blood pressure improved significantly only in the CCR group.

Dietary intake data showed substantial calorie reduction in both groups, with a greater decrease in the CCR group. The percentage of protein intake relative to total energy intake increased in both groups, although no direct correlation was observed between protein intake and fat-free mass preservation.

Dropout rates differed, 19% in the CCR group and 0% in the ICR group. This suggests time-restricted eating may be easier to follow in the short term, although interpretation should remain cautious given baseline differences, different physical activity assessment methods, and the short three-month duration.

Formal exploratory regression analyses showed no statistically significant differences between diets for body composition, resting energy expenditure, glycemic outcomes, or cardiometabolic measures, with dropout rate being the primary observed difference.

Conclusions

Both CCR and ICR diets significantly improved body composition in adults with type 2 diabetes and overweight or obesity over three months, without evidence of excessive loss of fat-free mass. While resting energy expenditure declined only in the CCR group, metabolic improvements were observed with both approaches. The lower dropout rate in the ICR group suggests greater short-term feasibility, though longer-term adherence remains uncertain. Longer-term randomized controlled trials are needed to determine the durability, metabolic adaptations, and clinical outcomes associated with these dietary strategies.