Changes in alanine aminotransferase and body composition and metabolic factors among individuals receiving medical health checkups

Aim To examine the relationship between changes in alanine aminotransferase (ALT) and those in body composition and metabolic factors in participants receiving medical health checkups (4350 men [mean age 52.5 years] and 5398 women [mean age 50.5 years]) Methods We divided the participants into four types based on their ALT value at baseline and 1 year: A, ALT ≤30 (baseline) and ≤30 (1 year); B, ALT ≥31 (baseline) and ≤30 (1 year); C, ALT ≤30 (baseline) and ≥31 (1 year); and D, ALT ≥31 (baseline) and ≥31 (1 year). The change in each body composition‐related parameter (waist circumference, fat mass, fat‐free mass, fat mass to fat‐free mass ratio, etc.) after 1‐year was defined as Δ. Results The mean changes in waist circumference (cm) in the four types (A, B, C, and D) were −0.33, −1.54, 0.66, and −0.29 (overall p < 0.0001) in men, and −0.19, −0.90, 0.30, and 0.090 (overall p < 0.0001) in women. The mean changes in fat mass (kg) in the four types were −0.027, −0.86, 0.62, and 0.092 (overall p < 0.0001) in men, and 0.0067, −0.48, 0.39, and 0.063 (overall p < 0.0001) in women. The mean changes in fat‐free mass (kg) in the four types were −0.028, −0.55, 0.42, and −0.034 (overall p < 0.0001) in men, and −0.0091, −0.34, 0.12, and −0.045 (overall p = 0.0012) in women. The mean changes in fat mass to fat‐free mass ratio in the four types were −0.00042, −0.0120, 0.00837, and 0.00171 (overall p < 0.0001) in men, and −0.00013, −0.00817, 0.00730, and 0.00628 (overall p < 0.0001) in women. Conclusion A decrease in ALT to ≤30 IU/L may be associated with improved body composition balance, but caution should be exercised for the decrease in muscle mass.