As discussed previously, different brain regions are affected by HFD; for example, in the hypothalamus, where the earliest activation occurs due to obesity (from day 1), the microglia lose their phagocytic capacity, while in the hippocampus, the expression of IBA1, CD45, CD68, MHC-II, and IL-1β increases (Milanova et al. 2021). Here, IL1B is linked to obesity due to melanocortin 4 receptor deficiency.