Reducing the daily eating window from ≥14 hours to a self-selected 10-hour window may lead to weight loss and a decrease in metabolic risk factors such as waist circumference, blood pressure, atherogenic lipids, and hemoglobin A1C (HbA1c), according to study results published in Cell Metabolism. Known as time-restricted eating, this emergent dietary intervention focuses on a consistent daily cycle of feeding and fasting to support circadian rhythms.
Patients were recruited from clinics affiliated with the University of California at San Diego and had a diagnosis of metabolic syndrome and a self-reported eating interval of ≥14 h/d. Complete data were available for 19 participants who finished the time-restricted eating intervention (13 men; 63% non-Hispanic white; mean age, 59±11.14 years), which required that patients maintain a shortened daily eating window of approximately 10 hours and nightly fasting. The majority of patients (84%) were taking ≥1 medication, with high statin (79%) and antihypertensive (63%) use. Most participants were clinically obese, with a body weight of 97.84±19.73 kg and a body mass index of 33.06±4.76 kg/m2.
Participants were trained to use the Salk Institute’s myCircadianClock smartphone application to log their caloric intake during a 2-week baseline period and 12 weeks of intervention. They also used a continuous glucose monitor and an Actiwatch at various time points during the study.
Investigators observed significant reductions in body weight from baseline (-3.30±3.20 kg [-3%]; P =.00028), body mass index (-1.09±0.97 kg/m2 [-3%]; P =.00011), and percent body fat (-1.01%±0.91% [-3%]; P =.00013) in the study cohort. A significant reduction in visceral fat rating (-0.58±0.77 [-3%]; P =.004) and waist circumference (-4.46±6.72 cm [-4%]; P =.0097) indicated that some of the body fat loss was from the abdominal area. Waist circumference was correlated with change in eating interval (P =.005), change in weight (P =.017), and combined change in eating interval and weight (P =.004).
Time-restricted eating was also linked to reductions in atherogenic lipid levels and blood pressure. Participants experienced significant reductions in total cholesterol (-13.16±24.29 mg/dL [-7%]; P =.03), low-density lipoprotein cholesterol (LDL-C; -11.94±19.01 mg/dL [-11%]; P =.016), and non-high-density lipoprotein cholesterol (-11.63±22.94 mg/dL [-9%]; P =.04). Change in high-density lipoprotein cholesterol was not significant, although it trended lower.
Of particular interest was the reduction in LDL-C, given the cohort’s high use of statin therapy. “Treating LDL-C to a target of <100 mg/dL by adding medications to statin therapy is recommended in treating high-risk participants for primary prevention of [cardiovascular disease],” wrote the researchers. “Our ability to do this with [time-restricted eating] as ‘add-on’ therapy to statins is intriguing and, given its potential clinical implications, warrants further investigation.”
Significant reductions in systolic (-5.12±9.51 mm Hg [-4%]; P =.041) and diastolic blood pressure (-6.47±7.94 mm Hg [-8%]; P =.004) corresponded to those expected by weight loss through other means. Similar to the result of lower LDL-C levels, the reduction was notable considering 63% of participants were on antihypertensive therapy.
Relative to glucose regulation, time-restricted eating was linked to improvement in fasting glucose (-5.7±13.54 mg/dL [-5%]; P =.081), fasting insulin (-3.6±8.01 mIU/mL [-21%]; P =.064), and HbA1c (-0.14%±0.29% [-2%]; P =.058). Of the 19 participants, 12 had an HbA1c of ≥5.7% and/or elevated fasting glucose (≥100 mg/dL) at baseline. In these patients, there was a greater reduction in HbA1c (-0.22%±0.32% [-3.7%]; P =.04) and trends toward improvement in fasting glucose (n=12; -8.67±16.26 mg/dL [-7.6%]; P =.092) and mean glucose (n=10; -10.08±16.06 mg/dL [-9.4%]; P =.078), as measured by continuous glucose monitoring.
In addition to overt metabolic syndrome risks, time-restricted eating also affected sleep. Using the Pittsburgh Sleep Quality Index and the myCircadianClock app to assess subjective sleep satisfaction, patients reported restful sleep on 69.88%±25.61% of days at baseline. This number increased by 23% to 88.16%±21.89% (P =.019). However, time-restricted eating did not lead to significant changes in objective measures of sleep efficiency or duration.
Although patients were not instructed to modify their caloric intake, there was a slight decrease during the intervention (1792.00±578.08 calories vs 1990.59±644.89 calories at baseline [-8.62%±14.47%]; P =.007). There were no significant changes in physical activity during the 12-week study period.
The unblinded single-group pilot study was limited by its small sample size and heterogeneity in medication use.
“We found this [time-restricted eating] intervention improves cardiometabolic health for patients with metabolic syndrome receiving standard medical care including high rates of statin and anti-hypertensive use. [Time-restricted eating] is a potentially powerful lifestyle intervention [without an overt attempt to change physical activity or diet quality or quantity] that can be added to standard medical practice to treat metabolic syndrome,” investigators concluded.
Disclosure: One study author declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.
Wilkinson MJ, Manoogian ENC, Zadourian A, et al. Ten-hour time-restricted eating reduces weight, blood pressure, and atherogenic lipids in participants with metabolic syndrome [published online December 5, 2019]. Cell Metab. doi:10.1016/j.cmet.2019.11.004