Time-restricted eating outperforms calorie counting in weight loss for type 2 diabetes patients

By Neha MathurOct 31 2023Reviewed by Benedette Cuffari, M.Sc.

In a recent article published in Jama Network Open, researchers discuss the findings of a six-month-long randomized clinical trial (RCT) evaluating time-restricted eating (TRE) without calorie counting as an alternative strategy to daily calorie restriction (CR) for reducing body weight and regulating glucose levels in patients with type 2 diabetes (T2D).

Study: Effect of Time-Restricted Eating on Weight Loss in Adults With Type 2 Diabetes: A Randomized Clinical Trial. Image Credit: Serenko Natalia / Shutterstock.com

Background

Current estimates indicate that T2D affects about 10 million people in the United States alone. Globally, T2D cases are increasing, with some researchers projecting that up to one in three U.S. adults will be affected by this condition by 2050.

Although CR is the most commonly prescribed intervention in T2D, it is often tedious to follow and difficult to adhere to, thereby limiting patient compliance. Thus, there remains an urgent need for alternative intervention strategies for T2D, such as TRE.

To date, studies investigating the effects of TRE in patients with T2D are limited. In one study investigating a 10-hour TRE intervention for 12 weeks in 120 obese adults with T2D, researchers observed that the study participants lost about 3.5% body weight as compared to controls. Similarly, a nine-hour TRE intervention reduced body weight by 1.1% in just three weeks in a small cohort of 14 obese men and women with T2D. 

About the study

In the present study, researchers recruited 75 adults between 18 and 80 years of age with a previous diagnosis of T2D. Each study participant was randomly placed into the CR, TRE, or control group. All included participants had hemoglobin A1c (HbA1c) levels between 6.5-11% g/dl and body mass index (BMI) values between 30-50 kg/m². 

The TRE group participants ate with no restrictions on the type or quantity of food during the eight-hour eating window between 12:00 and 8:00 p.m. daily. However, this group fasted for 16 hours from 8:00 p.m. to 12:00 p.m. the following day, during which they only consumed water and energy-free drinks. CR group participants reduced their calorie intake by 25% of their baseline energy requirements throughout the trial. 

All participants met with the study dietitian from baseline to the third month, who maintained a record of their body weight, diet adherence, medication changes, and adverse events. TRE and CR group participants also adhered to their physical activity routines and healthy food choices, thus conforming to American Diabetes Association (ADA) guidelines.

TRE and CR group participants also followed a medication management protocol, which mandated that they reduce their dose of short-acting insulin by 50% while not changing the dose of long-acting insulin and discontinuing sulfonylureas when baseline HbA1c levels were below 7%.

However, if HbA1c levels exceeded 7% up to 8.5%, the dose of sulfonylureas was reduced by 50% while not changing the long-acting insulin dose and reducing the short-acting insulin dose by 10%. When baseline HbA1c levels exceeded 8.5%, all medication doses remained the same.

As the primary outcome, the researchers measured the percentage change in body weight among the TRE, CR, and control groups by six months. Other outcomes included time in the glycemic range, average glucose level, HbA1c levels, body composition, medication effect, blood pressure (BP), heart rate, plasma lipid profile, dietary intake and adherence, physical activity (PA), and adverse events.

Dual-energy x-ray absorptiometry was used to measure body composition, whereas the automated self-administered 24-hour (ASA-24) dietary assessment was used to measure dietary intake. Daily footsteps were quantified by PA levels.

All participants wore a continuous glucose monitor (CGM) or tested their blood glucose levels using a glucose monitor for a minimum of 10 days at baseline, as well as three and six months. This allowed the researchers to detect hypoglycemia or hyperglycemia, reflected by glucose levels less than 70 mg/dL or over 180 mg/dL, respectively.

Study findings

The current RCT analyzed data from 75 participants, with 25 participants in each group, TRE, CR, and control. Women comprised 71% of the study cohort, whereas 53% of the study cohort were non-Hispanic Black. The average age, BMI, and HbA1c levels of these participants were 55 years, 39 kg/m², and 8.1% g/dl. 

The eight-hour TRE intervention was more effective for weight loss than CR at -3.6% and -1.8%, respectively. BMI also decreased in the TRE group by month six but not in the CR group. HbA1c level reductions were similar in the TRE and CR groups relative to controls at -0.90% and -0.94%, respectively.

Both TRE and CR groups were associated with comparable reductions in waist circumference but not visceral fat mass relative to controls. Notably, visceral fat mass is a robust factor associated with changes in glycemic control.

CR typically reduces body weight by 4-7% after six months. However, participants in the CR group in this trial reported greater difficulty with adhering to their intervention relative to TRE group participants, who easily adhered to their intervention and achieved higher overall energy restriction. It is likely that the study participants previously tried calorie counting but found TRE easier, which might have increased overall adherence in the TRE group.

There were no reports of any serious adverse events or influence of medication in any group.

Conclusions

Despite its relatively short duration, the current RCT addressed some critical knowledge gaps about intervention strategies that might improve the health of people with T2D. Importantly, the study population was representative of Hispanic and non-Hispanic Black adults for whom TRE could be a highly appealing weight loss approach while continuing to consume familiar foods.

TRE was safe in patients who depend on diet or medications to control their T2D. However, for people using sulfonylureas or insulin, its adoption will require medication changes and continuous monitoring, particularly during the initiation of the intervention.

Overall, this trial demonstrated that eight-hour TRE without calorie counting was an effective alternative diet strategy for weight loss and reducing HbA1c levels for adults with T2D. Larger RCTs with longer follow-up durations are needed to confirm these findings.