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What Causes What
MECHANISM? CONDITIONAL

Eating window (time-restricted eating) → Insulin resistance (HOMA-IR)

Higher Eating window (time-restricted eating) moves Insulin resistance (HOMA-IR) only in some conditions. Read the mechanism.

In eight men with prediabetes, a supervised 6-hour early eating window improved insulin sensitivity without weight loss; later RCTs show the effect depends on clock time and calories.

Randomized trial · Moderate · N=8

Supported by an experiment or a tightly identified design. Read the caveats.

Mechanism

Insulin sensitivity and beta-cell response run higher in the morning than in the evening. Sutton's group treated that as a reason to finish dinner before 3pm and stretch the overnight fast, then matched food and held weight so the window could not smuggle a calorie deficit. Mean insulin during a 3-hour OGTT fell 26 mU/l. The incremental AUC ratio, their insulin-resistance index, fell 36 percent. Morning glucose did not move. Xie compared two 8-hour windows in people without obesity. Early (6am to 3pm) lowered HOMA-IR. Mid-day (11am to 8pm) did not, even though both arms cut calories. That is a clock effect, not a fasting-hours effect. When calories are the comparison, the window often adds nothing. Liu's year-long 8am-to-4pm TRE plus calorie restriction moved HOMA-IR about as much as calorie restriction alone. Maruthur's isocaloric 10-hour window, with most calories before 1pm, did not beat a usual eating pattern on HOMA-IR or OGTT glucose. Lowe's noon-to-8pm 16:8, a late window with no calorie target, left fasting insulin, HOMA-IR, and HbA1c unchanged against three structured meals. Manoogian's TIMET trial in metabolic syndrome found a 0.10 percent HbA1c edge for an 8-to-10-hour personalized window on top of counseling. Fasting insulin and HOMA-IR estimates included the null. Isolated TRE in Haganes did not move OGTT glucose AUC. The HbA1c change sat on TRE plus interval training.

Caveats

Sutton enrolled eight men and did not match the pre-test fast (about 18 hours on eTRF versus 12 hours on control). An acute fast can worsen insulin sensitivity, so the improvement may be conservative. The sample is small and male. Sequence effects after washout were real for insulin. Lowe's metabolic labs were an in-person subset of 50. Liu is available here only as an abstract. HOMA-IR at 12 months differed by -0.5 (CI -1.4 to 0.4) between TRE plus calorie restriction and calorie restriction alone. Maruthur is available here only as an abstract, 41 people, 93 percent women, 93 percent Black, 12 weeks. Wilkinson is a 19-person single-arm pilot. HOMA-IR p=0.107. This edge is insulin resistance. Weight, blood pressure, and lipids are not this page. Eating dinner at 1pm is not a job and not a protocol.

Effect

qualitative. Sutton 2019: early 6-h vs 12-h, weight-stable; insulin AUC ratio -36% (p=0.005). Later RCTs mixed by clock time and calories.

Nodes

Lifestyle & environmentEating window (time-restricted eating)Biology & endocrinologyInsulin resistance (HOMA-IR)

Named confounders

Cite this page

What Causes What. “Eating window (time-restricted eating) → Insulin resistance (HOMA-IR).” https://whatcauseswhat.org/edges/e-tre-insulin (atlas updated 2026-09-02).

https://whatcauseswhat.org/edges/e-tre-insulin

Papers