That was only the experimental part of the study, which they did to explore what had been suggested by observational results[0] on a much larger group:
> A meta-analysis of several research studies has found differing results for the influence of seasonality on food intake[23]. We, therefore, analyzed data from a 3-year national nutrition survey of approximately 3,000 people. Using a generalized linear model adjusted for age, we found a significant interaction (P <0.001) between sex and season, revealing that men are markedly affected by solar radiation and its seasonal fluctuation compared to women (Fig. [1a]). Additionally, we averaged the monthly direct solar radiation data (KJ/m2) (Fig. [1a]) and found that men significantly increase energy consumption during the summer (March to September) as compared to winter (October to February) (2,188 Kcal versus 1,875 Kcal, respectively; p <0.001), while energy consumption in women remains the same (1,475 Kcal versus 1,507 Kcal, respectively; p = 0.79) (Fig. [1b] and Extended Data Fig. [1a]). Notably, since we found a significant increase in nutrients including: carbohydrates, proteins, fat, sodium, omega-3, zinc and iron in men during the summer (Extended Data Fig. [1a]), it is possible that the increase in men’s energy intake is due to an increase in appetite-stimulating nutrients such as sodium.
[0] https://www.nature.com/articles/s42255-022-00587-9#Sec2
[23] https://www.nature.com/articles/s42255-022-00587-9#ref-CR23
[1a, 1b] https://www.nature.com/articles/s42255-022-00587-9#Fig1