These days most of the advice is, You have to change nutrition, you have to eat a healthy diet, says Salk Associate Professor Satchidananda Panda. But many people dont have access to healthy diets. So the question is, without access to a healthy diet can they still practice time-restricted feeding and reap some benefit?
For the study to learn how forgiving time-restricted feeding is a group of 400 mice, from normal to obese, were given various types of diets and lengths of time restrictions.
- The benefits of time-restricted feeding showed up regardless of the weight of the mouse, type of diet and length of the time restriction to some degree.
- Regardless of whether the diets were high in fat, fructose, or fat and sucrose, mice that were given time restrictions of nine to 12 hours and consumed the same amount of daily calories as their unrestricted counterparts gained less weight than the controls.
- Variations in the time window in which the mice were allowed to eat a high-fat diet - including nine, 10 and 12-hour periods - all resulted in similarly lean mice. For a 15-hour group, the benefits conferred by time restriction became more modest.
Some of the time-restricted mice were allowed free access to high-fat meals on the weekends. Not only did they have less fat mass and gain less weight than the mice that were given a freely available high-fat diet the whole time, but they looked much the same as mice given access to food nine to 12 hours a day for seven days a week. This suggested that the diet can withstand some temporary interruptions.
Mice that had already become obese by eating a freely-available high-fat diet were restricted food access to a nine-hour window. Although they continued to consume the same number of calories they dropped bodyweight by five percent within a few days. Eating this way prevented the mice from further weight gain by about 25 percent by the end of the 38-week study compared to the group kept on the freely available high-fat diet. The researchers also compared mice given a more balanced diet and learned that the time-restricted mice had more lean muscle mass.
The fact that it worked no matter what the diet, and the fact that it worked over the weekend and weekdays, was a very nice surprise, added the studys first author Amandine Chaix, a postdoctoral researcher in Pandas lab. The therapeutic effect of time restriction was surprising, especially given evidence that nutritional deficiencies in early life can leave a lasting mark on animals metabolism.
Its an interesting observation that although the mice on a normal diet did not lose weight, they changed their body composition, Panda said. That brings up the question - what happens? Are these mice maintaining their muscle mass which might have been lost with free feeding, or are they gaining muscle mass?
In the future the researchers plan to investigate the effects of time-restricted eating in humans.