TLR4 and obesity due to melanocortin 4 receptor deficiency: However, other studies have described a higher feeding efficiency of the C3H/HeJ mice with increased adipose tissue mass and adipocyte hypertrophy (Poggi et al., 2007), an increase in body weight gain and adipose tissue mass in female TLR4−/− mice (Shi et al., 2006b) or no protection against obesity in male TLR4−/− mice (Shi et al., 2006b; Kim et al., 2007).