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Insulin sensitivity refers to how well the body’s cells respond to insulin – a critical aspect of maintaining healthy blood glucose levels. Lifestyle behaviors and dietary modification may help improve insulin sensitivity. Findings from a new study suggest that early time restricted eating improves insulin sensitivity.
Time-restricted eating is a form of daily fasting that aligns the eating and fasting cycles to the body’s innate 24-hour circadian system. People who practice time-restricted eating typically eat during an 8- to 12-hour daytime window and fast during the remaining 12 to 16 hours. Unlike intermittent fasting, which involves caloric restriction, time-restricted eating permits a person to eat as much as they want during the eating window.
The intervention study involved 16 healthy young men (average age, 23 years) who were moderately active and had BMIs between 18 and 27. After an overnight fast, the men underwent indirect calorimetry testing to determine their resting metabolic rate – the rate at which the body burns calories when at rest. The men wore continuous glucose monitors and tracked their dietary intake and physical activity.
After a one-week baseline period, the men’s metabolic response to a liquid test meal containing carbohydrates and protein was assessed. Eight of the men began the time-restricted dietary pattern, in which they consumed all their calories (eating whatever they wanted) during a window between 8 a.m. and 4 p.m. – considered “early” time-restriction. Nine months later, another group of eight men took part in the same process, but they ate whenever they wanted to, but their caloric intake was matched to that of what the men ate during the time-restricted eating period (which was about 400 calories per day lower than usual due to the limited time frame in which they ate). Both interventions lasted two weeks, after which both groups of men underwent metabolic testing again.
The men who followed the time-restricted eating pattern reduced their overall caloric intake and lost more weight, compared to the men who followed a calorie-restricted diet. Similarly, the men following the time-restricted diet experienced improvements in their whole-body insulin sensitivity as well as skeletal muscle uptake of glucose and branched-chain amino acids. The two groups of men had similar physical activity levels.
These findings demonstrate that early time-restricted eating improves insulin sensitivity and promotes weight loss in health men and has potential applications for interventions in people who are metabolically compromised. You can read about time-restricted eating in our overview article.
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