Bob Greene, Oprah’s personal trainer, has famously advised her (and her millions of devoted TV viewers and magazine readers) not to eat anything three hours before bedtime when trying to lose weight.
He may be on to something.
A new study reports that mice fed a high-fat diet only during the “sleep” phase of their daily cycle (which is daytime for these nocturnal critters) gained significantly more weight than mice fed the exact same diet only during their “awake” (nighttime) phase.
The mice fed at the “wrong” time during the six-week study had a 48 percent weight gain compared to the 20 percent gain experienced by the mice fed at the “right” time.
Furthermore, the mice fed when they’d typically be asleep gained about 8 percent more body fat than those fed during their normal wakeful hours.
“Simply modifying the time of feeding alone can greatly affect body weight,” concluded the Northwestern University researchers who conducted the study. The findings were published online this month in the journal Obesity.
Clocking up the calories
Why would meal timing matter? It has to do with circadian (daily) biological rhythms. As the study’s authors point out, recent research has shown that these internal “clocks” help regulate how the body uses energy.
Take the daily up-and-down rhythm of body temperature. Eating when body temperature normally dips (nighttime for humans, daytime for mice) has been linked to the increased storage of body fat. The daily rise and fall of hormones that help make us feel full, such as leptin, may also be a factor. These hormones may not be as active during the “wrong” feeding time, thus causing the mice (and perhaps us humans?) to overeat.
The human angle
Of course, people aren’t mice (insert your own joke here), but human studies have also hinted at an association between the timing of meals and weight gain. One study, for example, reported that people who skip breakfast are more likely to gain weight. Other research has found that people who work the night shift have a greater-than-average risk of being overweight.
Shift workers aren’t the only people who feast on food late into the night (as most of us know only too well). So could bedtime snacking be a contributing factor to our obesity epidemic? This study doesn’t answer that question, but it will certainly lead to other studies that may one day give us an answer.
In the meantime, following Bob Greene’s advice to not nibble on food after 7 p.m. or so may not be a bad idea.
Although, I hear that Oprah’s gained some weight this year.