Night owls may carry more body fat

Clinical takeaway: For patients who naturally stay up late, consider screening for breakfast skipping and late-night eating, then encourage shifting a meaningful portion of daily energy and nutrient intake earlier in the day.

Asking when patients eat—not only what they eat—may uncover a modifiable contributor to obesity and cardiometabolic risk.

In this cross-sectional study of 287 healthy New Zealand women aged 18 to 45 years, 34% were classified as evening types, 54% as intermediate types, and 12% as morning types. Compared with the combined morning/intermediate group, evening types had a median BMI of 31.4 versus 26.1 kg/m², average body fat of 36% versus 34%, and a higher android-to-gynoid fat ratio, suggesting greater central adiposity.

The biggest dietary difference was not total intake, but timing. Before 10 a.m., evening types consumed about 25% less energy, 25% less protein, and 25% less carbohydrate. After 8 p.m., the pattern flipped: they consumed roughly 58% more energy, 57% more protein, 63% more carbohydrate, and 55% more fat.

Evening types also obtained only about 9% of daily energy before 10 a.m., compared with 15% among earlier chronotypes; after 8 p.m., they consumed nearly 23% of daily energy, versus 11%. Their diets were also lower in fiber and several micronutrients, including folate, vitamins A and E, potassium, magnesium, calcium, and iodine.

Metabolically, evening types had higher triglycerides, insulin, leptin, and HbA1c, along with lower HDL cholesterol. Greater evening energy intake correlated with higher triglycerides, insulin, and HbA1c, while greater morning intake showed the opposite pattern.

As the authors put it, “not only what and when we eat, but also when we sleep” may shape metabolic health. Because the study was observational and chronotype overlapped substantially with ethnicity and socioeconomic factors, causation cannot be established.

Source: van der Merwe C, et al. (2026 July 13) Front Nutr. Chronotype and associations with dietary intake, meal timing, body composition, and metabolic biomarkers