Here’s Why When You Eat Makes a Difference

Whether you're trying to lose weight or boost overall health, when you eat matters.

Sure, there is some truth to the adage "you are what you eat." But, when you eat can be just as crucial. 

"Eating in tune with your circadian rhythms—[also known as] your body's inner clock that guides you to wake and sleep—automatically helps your health. You are getting fuel when you can actually use it and allowing your body to rest when it needs to," said Michael Roizen, MD, chief wellness officer of the Cleveland Clinic in Ohio. 

In that case, it does matter what time we eat. And ignoring those rhythms and eating at the wrong times—say, late at night—can increase the risk of heart disease, diabetes, and cancer.

If you want to understand meal timing a bit more, experts weighed in on the four fundamental guidelines to follow.

The Time You Should Eat

"Our bodies evolved to be primed for food during the day so that we'd have plenty of energy for survival," said Dr. Roizen. 

Your body is most sensitive to insulin during the day. Insulin is a hormone that moves glucose from your blood into most cells, like muscle cells. Your body uses glucose as fuel.

Your insulin resistance is highest at night when you're less active, and your body thinks it should be slumbering. As a result, Dr. Roizen said you end up storing most of the calories you consume in the evening as fat.

But between after-work spin classes and evening cocktail hours, you can't expect to get all your nourishment before the sun sets, especially during the winter when it gets dark as early as 4:30 p.m. 

A more realistic option: "Try to eat during a 12-hour window each day. For example, from 7 a.m. to 7 p.m., and then go on kitchen lockdown after that," said Pamela Peeke, MD, MPH, assistant professor of medicine at the University of Maryland in College Park, Md.

Don't Skip Breakfast

Some research suggests that morning eaters have lower blood pressure and cholesterol and less chance of having a heart attack or stroke than others.

There are also weight-loss benefits to eating breakfast. In one study, participants who ate a sizable breakfast (eggs, toast, and fruit) lost more weight after 12 weeks than those whose largest meal was at dinner. 

People who ate breakfast also had lower levels of:

  • Blood sugar
  • Insulin
  • Triglycerides
  • Hunger hormones

But if you can't stomach a full-fledged meal before noon, don't stress about it.

"The most important thing is to have something—even if it's small—in your stomach within two hours of waking up," said Tamara Duker Freuman, RD, author of The Bloated Belly Whisperer

Make sure your breakfast includes a mix of high-fiber carbohydrates and protein to help curb hunger. Duker Freuman added that two of her favorite choices are a slice of sprouted bread topped with egg and avocado or Greek yogurt and berries.

Have a Hearty Lunch

If a big breakfast isn't your thing, then lunch should be the main meal of your day. 

"Treat it how you'd normally treat dinner," advised Freuman. 

Fill half your plate with non-starchy vegetables, then divide the second half into lean protein and high-fiber carbohydrates like sweet potatoes or quinoa.

And don't skimp on lunch even if you had a hefty morning meal. Research has found that people who ate their main meal at lunch lost more weight than people who ate later.

"Ideally, you'll consume about 75% of your calories by 4 p.m.," said Freuman. 

 If you usually eat a salad, pair it with fiber and protein-rich lentil soup. Or add some nut butter and apple slices to your usual deli sandwich.

Eat a Light Dinner, and Then Close the Kitchen

Since your body is most insulin-resistant at night, you want to avoid carb-laden fares such as pasta or potatoes. Focus on a serving of lean protein paired with fiber-packed fruits and vegetables, advised Peeke. 

While earlier is better, if you occasionally eat at 8:30 p.m. or 9 p.m., that's fine. Just have a snack a couple of hours before, added Freuman, so you don't become so hungry that you will eat a huge meal before bed.

Whether you eat dinner earlier or later, try to avoid eating anything after that, advised Freuman. Late-night noshing has been linked to many harmful health effects, including an increased risk of type 2 diabetes and heart disease. 

Some evidence suggests that healthy adults who eat right up until bedtime have higher fasting blood sugar and cholesterol levels than those who stop eating at 7 p.m.

A Quick Review

In the end, it does matter when you eat. It would be best if you tried to eat a decent-sized breakfast and lunch, followed by a smaller dinner. 

Make sure you eat a well-balanced meal filled with protein, vegetables, and fiber. Also, if you avoid eating late-night snacks, this can decrease the risks of heart disease, diabetes, and cancer. 

So, watch what you eat. But remember to keep an eye on the clock, too. It will be time well spent.

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  1. Manoogian ENC, Panda S. Circadian rhythms, time-restricted feeding, and healthy agingAgeing Res Rev. 2017;39:59-67. doi:10.1016/j.arr.2016.12.006

  2. Carrasco-Benso MP, Rivero-Gutierrez B, Lopez-Minguez J, et al. Human adipose tissue expresses intrinsic circadian rhythm in insulin sensitivityFASEB J. 2016;30(9):3117-3123. doi:10.1096/fj.201600269RR

  3. St-Onge MP, Ard J, Baskin ML, et al. Meal Timing and Frequency: Implications for Cardiovascular Disease Prevention: A Scientific Statement From the American Heart AssociationCirculation. 2017;135(9):e96-e121. doi:10.1161/CIR.0000000000000476

  4. Jakubowicz D, Barnea M, Wainstein J, Froy O. High caloric intake at breakfast vs. dinner differentially influences weight loss of overweight and obese womenObesity (Silver Spring). 2013;21(12):2504-2512. doi:10.1002/oby.20460

  5. Madjd A, Taylor MA, Delavari A, Malekzadeh R, Macdonald IA, Farshchi HR. Beneficial effect of high energy intake at lunch rather than dinner on weight loss in healthy obese women in a weight-loss program: a randomized clinical trialAm J Clin Nutr. 2016;104(4):982-989. doi:10.3945/ajcn.116.134163

  6. Poggiogalle E, Jamshed H, Peterson CM. Circadian regulation of glucose, lipid, and energy metabolism in humansMetabolism. 2018;84:11-27. doi:10.1016/j.metabol.2017.11.017

  7. Penn Medicine News. Timing meals later at night can cause weight gain and impair fat metabolism.

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