One meta-analysis study of neutral research design quality reported that when metabolic rate is measured for 6 hours after moderate to large meal consumption reveal that 57% of the thermic effect of food has been expended at 3 hours, 77% at 4 hours and 91% at 5 hours (Reed, et al, 1996).  A second study of plus quality rating (Haugen HA, et al, 2003) in healthy adults (10 males and 24 females, 21-67 years) with varying kcal intakes (503±210 kcals/meal using dietary recall assessment and ventilated hood gas collection device) reports afternoon group mean thermic effect of food in the fourth hour (1598±34 kcals/day) was 6% above group mean morning, fasting RMR (1510±34 kcals/day) and would represent a 99 kcals/day misjudgment (95% confidence interval 74-130 kcals/24 hours) when extrapolated to 24 -hours.   When measuring five hours after eating, one study (Br J Nutr, Kinabo JL and Durnin VJGA, 1990) of plus quality research design (using a Douglas bag measurement protocol) reports that a 5-hour indirect calorimetry measure taken in 16 lean women, 18-40 years after consumption of 1-1200 kcal high carbohydrate (70% kcals from CHO) OR high fat meal (65% kcals from fat), a 5-hour postprandial group mean measure was above baseline.  When these women consumed only a 600 kcal high CHO or fat diet, a 5-hour group mean measure was above baseline basal metabolic rate, but much lower compared to the larger (1200 kcals) meals.   Therefore, a minimum fast of 5 hours after meals or snacks. 

• Grade I means there is Good/Strong evidence supporting the statement;
• Grade II is Fair;
• Grade III is Limited/Weak;
• Grade IV is Expert Opinion Only;
• Grade V is Not Assignable.
• High (A) means we are very confident that the true effect lies close to that of the estimate of the effect;
• Moderate (B) means we are moderately confident in the effect estimate;
• Low (C) means our confidence in the effect estimate is limited;
• Very Low (D) means we have very little confidence in the effect estimate.
• Ungraded means a grade is not assignable.