1. Neural control of skeletal muscle thermogenesis
Along with modulating energy-balance behaviors (e.g., food intake, physical activity), the brain also changes activation of the sympathetic nervous system (SNS). The SNS then increases heat generation, or thermognesis, in skeletal muscles in response to contextual stimuli indicating predator threat. This also increases the number of calories burned–essentially, the skeletal muscles use more fuel to perform the same work, dissipating calories as heat energy, increasing the temperature of the skeletal muscle. We are investigating how the brain spurs thermogenesis, specifically focusing on the ventromedial hypothalamus (VMH).
- Gorrell E, Shemery A, Kowalski J, Bodziony M, Mavundza N, Titus AR, Yoder M, Mull S, Heemstra LA, Wagner JG, Gibson M, Carey O, Daniel D, Harvey N, Zendlo M, Rich M, Everett S, Gavini CK, Almundarij TI, Lorton D, Novak CM (2020) Skeletal muscle thermogenesis induction by exposure to predator odor. Journal of Experimental Biology, 223 (Pt 8): pii: jeb218479. (PMID: 32165434; doi: 10.1242/jeb.218479)
2. Treatments for obesity in low-activity rats
With calorie restriction, along with weight loss, physical activity is suppressed. Moreover, for weight loss, daily food restriction is more effective in the more physically active rats (HCR) than in the obesity-prone sedentary rats (LCR). This could be partly due to physical activity—HCR are more active than LCR even during food restriction.
Because restricting daily caloric intake induces adaptive adaptations in physical activity and energy expenditure, it is difficult to maintain long-term weight reduction. Our data suggest that this would be even more difficult for those who are prone to obesity. We have found that a different type of energetic challenge produces better results. Intermittent fasting (IF)—providing food every-other day—results in long-term weight loss in rats. Moreover, IF induces more fat loss in the obesity-prone rats.
- Smyers ME, Koch LG, Britton SL, Wagner JG, Novak CM (2021) Enhanced weight and fat loss from long-term intermittent fasting in obesity-prone, low-fitness rats. Physiology & Behavior, 230: 113280 (PMID: 33285179; doi: 10.1016/j.physbeh.2020.113280)
- Mukherjee S, Koch KG, Britton SL, and Novak CM (2020) Aerobic capacity modulates adaptive thermogenesis: Contribution of non-resting energy expenditure. Physiology & Behavior, 225: 113048 (PMID: 32628949; doi: 10.1016/j.physbeh.2020.113048)
- Smyers ME, Bachir KZ, Britton SL, Koch LG, and Novak CM (2014) Physically active rats lose more weight during calorie restriction. Physiology & Behavior, 139C: 303-313. (PMID: 25449411)