Intermittent fasting 5:2 diet: What is the macronutrient and micronutrient intake and composition?

Intermittent fasting (IF) is a dietary intervention that has been investigated as an alternative weight-loss diet due to conventional approaches having poor long-term adherence. However, the macronutrient and micronutrient intake and composition of IF diets have been overlooked. The primary aim of this study was to describe the macronutrient and micronutrient intake of individuals following the 5:2 intermittent fasting diet (IF 5:2).

Thirty eight overweight and obese participants were included from two previous studies of IF 5:2. The participants selected included 27 males and 11 females, with and without Type 2 Diabetes. The dietary intervention, IF 5:2, consisted of two days per week fasting, either consecutive or non-consecutive, and five days per week of habitual intake. Prospectively completed 4-day estimated food records were used to assess macronutrient and micronutrient intake at baseline and week six. The 4-day records were weighted to give a mean daily intake during IF 5:2.

During IF 5:2 the median (25th, 75th quartile) daily macronutrient composition was 22 (19, 24)% from protein, 33 (29, 37)% from fat and 39 (36, 43)% from carbohydrates. The intake (g/d) of carbohydrates and fibre decreased significantly from baseline to week six (p < 0.001) as well as on fasting days compared to non-fasting days (p < 0.001). The intake of calcium, zinc, magnesium and potassium were lower than recommended guidelines. Sodium intake exceeded the suggested daily target. On fasting days, the percent of total energy from protein significantly increased from 21% to 25% (p = 0.02). Despite intake being unrestricted on non-fasting days the energy intake decreased by week six when compared with baseline.

The composition of IF 5:2 was a high protein, moderate fat, low carbohydrate diet with a low fibre intake. Some micronutrients have lower than recommended intake. However, overall IF 5:2 is a safe acceptable weight-loss diet strategy.