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Bicycling

Eating Protein Late at Night Can Have This Unexpected Impact

Elizabeth Millard
3 min read
Photo credit: Andrei Kravtsov - Getty Images
Photo credit: Andrei Kravtsov - Getty Images

From Bicycling

  • According to research presented at The Physiological Society’s recent virtual conference, consuming protein later at night and again when you wake up can result in higher blood sugar levels in the morning.

  • It may be advisable to move your late evening workouts up a bit so you’re not eating so close to bedtime.


After an evening workout, you may think to eat a protein-filled dinner for a muscle-booster before going to bed. And if you go for a ride the next morning, you may consider some protein as part of a pre-ride meal.

However, research presented at The Physiological Society’s recent virtual conference showed a surprising result—that approach may actually increase your blood sugar level.

Researchers asked 15 healthy young men and women to test their blood sugar levels at different points after eating. In one session, they were awakened at 4 a.m., and asked to either drink water or eat a snack that contained 63 grams of whey protein.

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The people went back to sleep, and five hours later, they all ate a standard porridge breakfast with blood samples collected two hours later to check glucose response. A week later, they returned and swapped—those who’d had water now had the protein, and the protein group had water. That was followed by the same routine of going back to sleep, having a regular breakfast, and checking glucose levels a few hours after.

The researchers found that the people who consumed 63 grams of protein in the middle of the night had significantly higher blood sugar levels after eating breakfast a few hours later than when they only had water overnight.

Although the research sample size was small and the timeframe was short, lead presenter Eleanor Smith, M.Sc., of Liverpool John Moores University and the University of Bath, told Runner’s World that more studies should be done on this since the results were unexpected.

A snack a few hours before a meal can help control blood sugar levels, so researchers anticipated that would happen here as well—except the opposite showed to be true.

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“We wondered if waking up at night to consume some protein might keep blood sugars lower the next morning,” she said. “Surprisingly, however, the blood sugar response to breakfast was higher when participants consumed protein at 4 a.m. rather than plain water.”

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Although the reason for this still needs to be explored, she suggested one explanation may be that the body doesn’t expect or need much food at night, so instead of using protein the way it would during the day, the body turns that protein into sugar instead. More research will also explore whether there’s a difference between eating protein earlier in the evening versus that late-night/early-morning consumption, but Smith said it’s likely the results would be the same.

“This may result in the body having more carbohydrates already available upon waking, such that the energy in the breakfast can less easily be used or stored, so it builds up more in the blood,” she said.

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Does this mean you need to skip a pre-workout snack or meal if you’re an early morning exerciser? Not really, since exercise lowers blood sugar—which is why the American Diabetes Association recommends getting physical activity after meals. But it may be advisable to move your evening workouts earlier so you’re not consuming protein so close to bedtime.

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