Can Your Body Clock Help You Lose Weight?

by Jodi Helmer
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Can Your Body Clock Help You Lose Weight?

When it comes to weight loss, paying attention to your internal clock could be as important as counting steps or setting the stopwatch on your fitness tracker.

Your circadian rhythm, the 24-hour clock that governs bodily rhythms — ranging from sleep-wake cycles and body temperature to hormones and digestion — also appears to have an impact on your weight.

Changing the timing of sleep, meals and workouts can wreak havoc on circadian rhythms. In contrast, sticking to a specific schedule — and timing when you consume most of your calories — can aid in weight loss.

“We can optimize our performance by trying to achieve a match between our body clocks and time of day that we perform various tasks,” explains Robert L. Matchock, PhD, associate professor of psychology at Pennsylvania State University.  

BIG BREAKFAST, SMALL DINNER

Research published in the journal “Obesity” found the timing of your biggest meal was linked to the number on the scale. Study participants who consumed 700 calories at breakfast, 500 calories at lunch and 200 calories at dinner for 12 weeks lost more weight and had a greater reduction in waist circumference than those who ate 200 calories at breakfast, 500 calories at lunch and 700 calories at dinner. The researchers noted that eating a bigger breakfast also helped reduce fasting glucose, insulin and insulin resistance, which could lead to a decreased risk of Type 2 diabetes.

A 2017 study reported similar findings, noting that those who ate a heavier meal at lunch lost 25% more weight than those who ate a heavier dinner — despite similar nutrient and caloric intakes.  

Kristen Knutson, PhD, associate professor of neurology at the Feinberg School of Medicine at Northwestern University, admits that the link between circadian rhythm and weight gain is not fully understood but posits, “This association may be related to eating at the ‘wrong’ time, that is, when your body is not expecting you to eat. It could also be that eating in the evening impairs sleep, which has been associated with impairments in metabolism.”

TIMING AND REGULARITY MATTER

Shifts in the circadian system may also impact glucose tolerance, impairing your ability to lower blood sugar after an evening meal and causing your body to burn just half of the calories two hours after an evening meal that it does after an identical earlier meal.

In a new study, published in The American Journal of Clinical Nutrition, researchers examined data from 110 adults and found that eating late in the day increased the risk of metabolic syndrome, noting that those with the highest BMI and body fat percentages consumed most of their calories late at night. Based on their findings, researchers suggested that eating your last meal several hours before bed gives your body time to digest, decreasing the risk of storing fat.

“Sleeping and eating at regular times each day helps to keep circadian rhythms synchronized,” Knutson says. “Avoid eating in the evening and at night, and even give yourself a time window for eating food — for example, 8 a.m. to 8 p.m.”

While honoring your circadian rhythms is important, it’s not license to overeat. Regardless of when you eat, losing weight still requires counting calories but consuming them at certain times can be helpful.

“Jumping all around the clock from one day to the next (or from weekdays to weekends) is hard on the body’s circadian rhythms,” says Knutson. “Keeping a regular schedule of sleep, meals and exercise will help to optimize health.”

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  • Laura Lynds

    I’m a nurse who works 12 hour shifts. I work 2 day shifts, then 2 night shifts, then 4 days off. Everything I read about weight loss talks about how important it is to sleep 8 hours every night. To eat regularly and exercise regularly. Is there some kind of plan that someone can come up with that would accommodate my schedule? After all, there are a lot of us who do shift work and find it difficult to stay healthy when our lives are all over the place.

    • Bev M

      This is entirely based on anecdotal evidence (my own), but this trying to fit everyone in the same sleep box, health-wise, doesn’t work. I actually gain weight and can’t sleep when I eat breakfast. And sleeping 8 hours a night being healthiest is a total myth. My body clock does not work that way. I cannot force myself to sleep 8 hours a night. My body will only stay asleep for 6 hours a night.

      • Donnalee Lee

        Buy a sleep tracker, monitor your current sleep for 1 week, look for when your body enters deep sleep. Then change up things to go sleep to with 2 hours of dusk, waking within 30 min of dawn. If you work shift work, create dusk and dawn by turning your lights to low within 30 min of when you want to sleep, and make sure your room is pitch black. When you wake up, if it’s dark outside, turn on a couple of lights in the house as you get ready, or set lights on a timer to turn on within 10 min of your alarm. Look at your sleep tracker, you should be hitting deep sleep with in 10 min of bedtime and in regular sleep 10 min before waking. Then adjust your bedtime to 10 min before your pattern shows you are in deep sleep. It will take a couple of weeks to change your habits. When you work shifts, you should still stay close to the “night pattern on your off days. You need to hit 40% deep sleep a night in order to be rested….even if it’s only 6 hours

    • Bron

      I’m a ED doctor. You can’t really change the times you sleep with shift work but that’s ok.
      – your goal should be not to let your body clock move too much, so you can enjoy your days off without needing recovery time.
      – the best way to do this is to not change meal times drastically. The circadian rhythms associated with eating are much stronger than those associated with light.
      – so always have a big breakfast and a big dinner at the same time, regardless of whether you are on days, evenings or nights. Then just add in a smaller meal or snack wherever it fits. The hard bit is not eating during night shift, but you shouldn’t get too hungry if you stick to this.
      – I’ve been doing this for years and can swap back to normal sleeping directly after night shift. If I cave and eat the junk food around at night time I pay for it later, waking up in the middle of the night on my days off.
      – having a big carb heavy breakfast when you are hungry after night shift helps you sleep better too. On nights I often just have the two bigger meals.

  • Therese

    My daughter lost over 75 pounds over the past year. The biggest dietary change she made was to eat nothing after 5 pm.

    • Mary Lou Cox

      This works for me too, except nothing after 3pm. At 70, not as much activity as I used to do. I can eat almost anything all morning long, sweets, pie, pizza, chocolate, but need to stop at 3pm. Love this but the hubby gets hungry sometimes. LOL

    • Isabelle Cloutier

      May I ask at what time she goes to bed?