Prolonged Overnight Fast, Energy Metabolism and Skeletal Muscle Anabolic Sensitivity

There is a growing interest in the cardiometabolic benefits of various intermittent fasting paradigms (such as alternate day fasting and the 5:2 fast diet), where periods of normal energy intake are punctuated by periods of energy restriction or fasting. A recent alternative to these protocols is time-restricted feeding (TRF), which limits daily food/energy intake to a narrow window (typically 8 to 10h). The major strength of TRF is that it extends the duration of overnight fast without limiting normal calorie intake. Recent evidence from both animal and human studies have shown that habitual daily periods of fasting of as little as 16h can reduce fasting insulin and triglycerides levels, protect against excessive body weight gain in response to high fat and sucrose diets, better maintain fat-free mass, and improve beta-cell responsiveness. We recently completed a 2-week TRF intervention study using the 8h fed (between 8am and 4pm)/16h fast protocol in healthy individuals and found improvements in insulin sensitivity and skeletal muscle uptake of branched chain amino acids. As we did not make measurements of muscle protein synthesis, it is not known whether a single episode of prolonged overnight fast (~16h) is sufficient to elicit improvements in insulin sensitivity and stimulate skeletal muscle protein synthesis in response to dietary protein ingestion. The aim of the proposed study is to investigate the effect of prolonged overnight fast (16h vs. 10h) on postprandial energy metabolism and skeletal muscle protein synthesis in healthy humans.

Inclusion criteria

• Male
• 18-35yrs
• healthy
• non-smoking
• physically active
• no excessive weight loss in past 6 months
• body mass index between 18 and 27 kg.m-2

Exclusion criteria

• body mass index under 18 and over 27 kg.m-2
• sedentary
• screening bloods out of range
• excessive weight loss in the past 6 months
• irregular eating patterns