Background: Obesity is a common cause for morbidity and mortality in the modern world. High-fat-diet (HFD) feeding in rodents leads to elevated body weight and adiposity. We aimed to investigate the behavioural changes in food intake with the progression of HFD-induced obesity.
Methods: Male C57BL/6 mice (n=66, 8weeks old) were fed ad libitum either a standard laboratory diet (SLD; 14%kJ from fat) or HFD (60%kJ from fat) for 1, 2, 4, 8, 10 or 12 weeks (n>5/group). A group of SLD and HFD mice (n=8/group) were housed in Promethium metabolic monitoring cages for 12 weeks continuous monitoring of eating behaviour.
Results: SLD and HFD fed mice gained weight over the 12weeks (Two-way-ANOVA (P<0.0001); Week-effect) dietary period. At 8, 10 & 12weeks, HFD-mice gained significantly more weight compared to SLD-mice (P<0.01). Ten and twelve week HFD-mice had greater gonadal fat pad mass compared to SLD-mice (P<0.0001). Total daily food consumption (grams) was not different between SLD and HFD groups. Despite this, feeding behaviour was altered in the HFD-mice. From weeks 1-8, dark phase meal number was lower in HFD compared to SLD-mice (P<0.05), likely due to fat-induced satiety. However, the meal number was not different at weeks 10 &12 between SLD and HFD groups, suggesting loss of the fat-induced satiety signal. There was an increase in dark phase meal size at weeks 2 & 4 in HFD compared to SLD-mice (P<0.05), with no differences observed at any other time points. HFD-feeding led to greater total energy consumption per meal during weeks 1-10 (P<0.05), and total daily energy intake in weeks 2, 4 and 12 (P<0.05) compared to SLD-mice.
Conclusion: HFD-feeding in mice led to altered eating behaviours as early as 2 weeks. This occurred prior to changes in body weight suggesting that diet rather than adiposity is driving these behaviours.