The effect of time-restricted eating accompanied by weight loss on thyroid function in adults with type 2 diabetes.

Abstract

Context: Time-restricted eating (TRE) is a lifestyle intervention associated with beneficial cardiometabolic effects. The impact of TRE-induced weight reduction on thyroid hormonal responses is not well elucidated.

Objective: To evaluate the effects of TRE accompanied by weight loss on thyroid function in adults with obesity and type 2 diabetes (T2DM).

Methods: We performed an exploratory analysis of a randomized, crossover, open-label study in adults with obesity and T2DM who underwent 2 dietary interventions: TRE and standard lifestyle. Each intervention period lasted 6 weeks. Thyroid function was assessed by TSH, free T4 (fT4), free T3 (fT3), and reverse T3 (rT3).

Results: Thirty-nine participants without known thyroid disease (age 56.3 years, 35.9% male, body mass index 32.4 ± 5.7 kg/m²) were included. TRE induced significant weight loss (-2.93 kg) compared to the standard lifestyle period (0.59 kg) (mean differences between intervention periods of -3.50 kg ± 2.9; P < .001). Despite this robust weight-lowering effect, there were no significant differences in TSH (0.49 mUI/L ± 3.0; P = .32), fT3 (-0.57 pmol/L ± 2.7; P = .19), fT4 (fT4 -0.55 pmol/L ± 3.8; P = .38), and rT3 (-0.94 ng/dL ± 5.9; P = .350) between intervention periods. Reinforcing these findings, there was no treatment effect interaction on any thyroid function test evaluated. In addition, there was no significant change in the fT3: fT4 and fT3:rT3 ratios between treatment interventions.

Conclusion: Despite inducing significant weight loss, TRE did not exert a significant effect on thyroid function in individuals with obesity and early T2DM.