Here’s another reason to hate Daylight Savings Time:
Researchers at Vanderbilt University have proven that insulin production is tied to your internal circadian clock, and disruption of that clock can lead to increased insulin resistance and obesity. The results of the study were published in the journal Current Biology earlier this year.
While researchers had long suspected that disruption of the body’s natural circadian rhythm could lead to insulin resistance and increased risk of obesity, they hadn’t found definitive evidence tying insulin production to the body’s circadian clock until this year. The team of researchers examined insulin sensitivity in mice, who, being nocturnal, have the mirror opposite circadian rhythms of humans.
Before we get to the results, here’s a mouse metabolism primer: Normally, insulin sensitivity in mice is cyclical, tied to whether the rodents are active or inactive. Their bodies are more sensitive to insulin when they are active, meaning they burn more glucose during that period. When they’re asleep or fasting, their bodies are more insulin-resistant, which allows the body to store energy as fat to use for later.
The researchers examined insulin resistance and circadian rhythms in two ways. One way was by examining garden-variety laboratory mice who lacked the gene for regulating internal circadian rhythms. These critters seemed locked in a 24-hour cycle of heightened insulin resistance, and thus packed on the ounces when fed a high-fat diet. Their insulin-resistance continued even when the mice were active. The researchers then introduced into the mice the protein that allows them to effectively regulate their circadian clocks; the rodents became less insulin-resistant and lost excess weight.
The researchers also disrupted the circadian rhythms of genetically “wild-type” lab mice by leaving them in a lighted environment 24/7. These mice also grew insulin resistant and gained more weight than wild-type mice living in an environment with darkness and light. The circadian-disrupted wild-type mice gained more weight even though they were fed less calories than their counterparts.
In both instances, both mice were more prone to diabetes and cardiovascular disease, all because of their bodies’ disrupted circadian clocks. Researchers say such increased insulin resistance is a leading reason why night-shift workers are prone to obesity and diabetes.
“Our study confirms that it is not only what you eat and how much you eat that is important for a healthy lifestyle, but when you eat is also very important,” said researcher Shu-qun Shi in an interview with a news publication for the university.
Other human-based research backs up this assertion. For example, NPR reported this summer on a Spanish study which found that dieters who ate most of their calories before 3 p.m. lost significantly more weight than those who ate most of their meals later in the day. Researchers for that study tracked 420 overweight or obese Spaniards and found that those who ate more of their calories earlier lost an average 5 additional pounds than their counterparts, and this despite both groups having the same calorie intake and activity level.
There are other ways to disrupt this circadian disruption. Tips to get your metabolism more in line with your circadian clock include:
- Get extra natural sunlight
- Avoid the midnight snack whenever possible
- If traveling, prepare for time zone changes by going to bed earlier or later in anticipation of the time zone shift. The same holds true for Daylight Savings Time shifts.