A September 2020 study by Scripps Research continues the research on the links between body temperature and calorie restriction.  The researchers said, 

“It's not easy to discern what's driving the beneficial changes of calorie restriction … Is it the reduced calories on their own, or the change in body temperature that typically happens when one consumes fewer calories? Or is it a combination of both?"

"The data we collected showed that temperature has an equal or greater effect than nutrients on metabolism during calorie restriction,"