A study of the benefits of intermittent fasting comparing male and female mice suggests intermittent fasting for women may have different results.
With the global obesity epidemic, a search for a simple but effective solution continues. Diets can be hard to follow, trying to figure portion size, macros, and calories. While exercise is great for physical fitness, it can sometimes be hard to complete if there are pre-existing health conditions that make movement difficult. One simple approach to weight loss is the age-old approach of fasting.
Fasting has been practiced since ancient times and has recently returned as an alternative method to achieve weight loss. There are different fasting methods such as intermittent fasting or alternate-day fasting, where no food is consumed for twelve or more hours. Also, time-restricted feeding, where food is only eaten during a specific eight to twelve-hour time frame, but there is no restriction on the type of food or the number of calories. However, scientists do not know which fasting type is best for specific people groups. For example, it is not known whether fasting for women will generate the same results as fasting for men.
To gain a better understanding of the effects of a short daily fast during the active phase, Australian researchers from the University of Sydney recently studied intermittent fasting in male and female mice. Their results were published in The Journal of Physiology.
Researchers studied the effects of a short, six-hour, daily fast, which lasted during the mice’s active phase (at nighttime). Seventy-two mice, made up equally of males and females, were studied for four weeks.
At the beginning of the study, the mice were allowed one week to get used to a twelve-hour dark, twelve-hour light cycle. Then they were placed in either the short daily fasting group or the group that could eat whenever they liked. In the short daily fasting group, food was removed from the mice’s cages for six hours in the middle of their active phase. The researchers measured the amount of food eaten and the mice’s body weights weekly.
At the end of the four-week period, the researchers gathered data on the mice’s body composition, the ability of the mice to metabolize glucose, their insulin levels, liver fat, genetic make-up, and protein levels. This data was statistically analyzed.
It was determined that there were significant differences in the ways that male and female mice responded to the short daily fasting period. While both male and female mice were similar in their eating patterns, there were distinct differences in fasting for females compared to males in their other responses.
During the fasting period, female mice stored more fat in their liver than male mice. Female mice were better at storing fats, and their bodies were better at using them. The researchers recommend further studies to determine whether the same effects would be experienced by humans. The study also suggested that fasting during the active phase could lead to disrupted circadian rhythms if food is then later consumed during the inactive phase.
Senior researcher, Samantha Solon-Biet, states that “by highlighting the different responses to fasting in male and female mice, we are showing the importance of including both sexes in preclinical studies”.
Written by: Rebecca K. Blankenship, B.Sc.
1. Patterson R, Laughlin G, LaCroix A et al. Intermittent Fasting and Human Metabolic Health. J Acad Nutr Diet. 2015;115(8):1203-1212. doi:10.1016/j.jand.2015.02.018
2. Freire T, Senior A, Perks R et al. Sex-specific metabolic responses to 6 hours fasting during the active phase in young mice. J Physiol (Lond). 2020. doi:10.1113/jp278806
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