While diet-induced obesity has been exclusively attributed to increased caloric intake from fat, animals fed a high-fat diet (HFD) ad libitum (ad lib) eat frequently throughout day and night, disrupting the normal feeding cycle. To test whether obesity and metabolic diseases result from HFD or disruption of metabolic cycles, we subjected mice to either ad lib or time-restricted feeding (tRF) of a HFD for 8 hr per day. Mice under tRF consume equivalent calories from HFD as those with ad lib access yet are protected against obesity, hyperinsulinemia, hepatic steatosis, and inflammation and have improved motor coordination. The tRF regimen improved CREB, mTOR, and AMPK pathway function and oscillations of the circadian clock and their target genes’ expression. These changes in catabolic and anabolic pathways altered liver metabolome and improved nutrient utilization and energy expenditure. We demonstrate in mice that tRF regimen is a nonpharmacological strategy against obesity and associated diseases.
These mice underwent a common form of intermittent fasting, namely a daily 8-hour feeding window followed by 16 hours of fasting. Despite eating the same amount of calories, they did not develop obesity, unlike the ad lib fed mice.
Ad lib eating could be a major cause of obesity in humans, in fact, the biggest cause. Before the obesity epidemic started, fast food was not as widely available, and certainly not 24 hours a day. People normally ate a regular dinner and then nothing until breakfast, resulting in a natural, daily cycle of 12 hours or so of intermittent fasting.
Along with low-fat diets, the modern paradigm also recommended frequent meals and snacking (“grazing”), which keeps insulin levels elevated and actually increases hunger. This was done on the dubious grounds of keeping blood sugar levels as some supposed optimum. Disastrous advice.
Perhaps the first thing to be done in obesity prevention, even before changes in type of food, is to limit eating to three (or fewer) meals a day. No snacking. To actually lose weight, intermittent fasting, such as the 16-8 schedule noted above, would be a good place to start.