You might've heard that breakfast is the most important meal of the day. If you just laughed at this seemingly old piece of advice, it might be time to rethink your nutrient timing — especially when it comes to carbs.
Carbs, short for carbohydrates, is one of the big three macronutrients (macros); the other two are protein and fat. They are all important nutrients in your diet, they all serve a purpose for health and none should be excluded completely from your diet.
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Some popular diet trends might suggest limiting your carbs altogether or counting the macros in your diet. If that all sounds like a lot of work, you may just be able to shift around your diet and see results. Think of it like the proverb, Eat breakfast like a king, lunch like a prince and dinner like a pauper. Those old prophets were on to something.
Why You Need Carbs, and the Best Time to Eat Them
Carbohydrates are essential — they're our major source of fiber, antioxidants, energy, vitamins and minerals. It's important to remember that you don't eat nutrients in isolation, you eat food. Many foods contain carbohydrates, mainly:
- All fruits
- All vegetables
- Whole grains
- Milk, cheese, yogurt
- Beans and legumes
- Sweets and candy
The 2020-2025 Dietary Guidelines for Americans recommend that carbohydrates comprise 45 to 65 percent of your diet. For a 2,000 calorie diet, that equals 900 to 1,300 calories (because each gram of carbs is 4 calories), or 225 to 325 grams of carbs each day.
If you're trying to maximize your metabolic burn, it won't hurt you to frontload some of your carb intake at breakfast and lunch, and taper back as the day goes on — ensuring you are still reaching your fruit, vegetable and fiber intake goals for the entire day.
While there is some emerging evidence in the field of chrononutrition about the benefits of meal timing, these studies do not focus on singular macronutrients, but on the whole diet concept.
What you eat is still just as important as when you eat. In other words, you can't justify eating pastries for breakfast every morning thinking that you might burn some extra calories — quality still matters.
Don't cut out carbs completely from the latter half of the day.
If your blood sugar gets too low, you may develop hypoglycemia. Low blood sugar can even affect how you sleep, so it's best to keep some carbs in your diet throughout the day. Symptoms of low blood sugar, per the U.S. Department of Health and Human Services, include:
- Dizziness and shaking
How Sleep Affects Your Metabolism
There is an emerging field of study called chrononutrition, which focuses on the interactions between circadian rhythm (aka, your sleep cycle), nutrition and metabolism.
Effects on Calories Burned
Multiple studies have found that eating more calories in the early hours of the day and less at night can spur weight loss, according to a May 2018 review in Nutrition Bulletin. It also seemed to improve fasting glucose, glucose tolerance and triglycerides.
One factor in this shift may be the effect on circadian rhythms and the thermic effect of food (TEF), sometimes called diet-induced thermogenesis. TEF is one of the components of energy expenditure with the other two being resting energy expenditure and physical activity.
TEF is the energy needed to digest and absorb nutrients. In other words, the calories burned from eating — yes, you read that right. You continue to burn calories after you eat.
It turns out that TEF is higher in the morning than in the evening, according to a small October 2015 study in Obesity. This means you're naturally burning more calories earlier in the day rather than in the evening. To keep this in context, TEF only accounts for about 10 percent of your total calories burned, so about 200 calories total if you're eating 2,000 calories a day.
On the flip side, there is no consensus to suggest that shifting your overall calorie intake, or simply one macronutrient, to the morning will have any effect on long-term weight loss, according to October 2019 research in Nutrients. The increase in TEF may be negligible and may not make a difference at all.
Effects on Blood Sugar
Glucose tolerance is higher in the morning. Researchers hypothesize that this has to do with the beta cells in your pancreas being most responsive in the a.m., per a July 2021 report in StatPearls. Your beta cells make insulin, and insulin is what's released to bring your blood sugar down.
So now, let's put that in context with carbohydrates. Carbs are broken down into molecules of glucose in your body, and those glucose molecules circulate in your blood. If you don't have diabetes, your pancreas secretes insulin to shuttle that glucose into cells to use for energy.
So if your beta cells are more responsive in the morning, you might want to take advantage of that.
Spacing Out Your Carbohydrates
You may have heard that if you eat carby foods for dinner, they'll directly turn into fat. That's not entirely true and is definitely more complicated than it sounds. Frankly, a statement like this can't be generalized for an entire population.
Some studies show that eating too many calories at night increases the risk for weight gain, but other research has not concluded the same, per an April 2015 report in Nutrients.
For some medical conditions and for athletes, having a snack with protein and carbs before bedtime can be advantageous and is encouraged. So, while eating a large meal right before bed is probably not in your best interest — think: heartburn and restless sleep — completely nixing food altogether may not be the right move either.
If you don't have any health conditions and would like to try and see how you feel by frontloading your carbohydrate intake earlier in the day, have a plan. If you're tracking about 225 grams of carbs per day, for example, you can try the following:
- A packet of plain instant oatmeal with 1/2 cup low-fat milk and 1 tablespoon honey: 60 g carbs
- 1/2 cup blueberries: 11 g carbs
- Coffee with 2 tablespoons creamer: 10 g carbs
- One banana: 27 g carbs
- 2 tablespoons peanut butter: 8 g carbs
- Sandwich with two slices whole-wheat bread, 4 ounces sliced turkey breast and one slice swiss cheese: 48 g carbs
- 1 cup strawberries: 13 g carbs
- 5-ounce container cottage cheese: 3 g carbs
- 1/2 cup raspberries: 8 g carbs
- Salad with 4 cups romaine, 1 cup tomatoes, 1 cup cucumbers, 4 ounces chicken breast, 1 hard-boiled egg and 2 tablespoons vinaigrette: 20 g carbs
- 4 cups air-popped popcorn: 19 g carbs
- One square dark chocolate: 10 g carbs
The Bottom Line
Most research points to the morning being the best time to eat carbs — if your goal is weight loss.
But everyone has different nutrition goals and timing your carbohydrate intake won't work for everyone. (This has mainly been studied in those who wish to lose a little weight.)
If you have any medical conditions, are on medications that affect your blood sugar, are pregnant or if you are an athlete, talk to your doctor or registered dietitian before you drastically cut back on carbs — at any time of day.
If you have type 1, type 2 or gestational diabetes, follow the nutrition advice given to you by your doctor or dietitian. Control of your blood sugar should be your top priority, and while chrononutrition may help, that is a decision that should be made with your doctor.
Also, remember that the science of eating around circadian rhythms is still new and there is much more to learn. Focus on quality, hunger cues and eat a sensible meal or snack if you're hungry — even if that's at night.
- Nutrition Bulletin: "The Big Breakfast Study: Chrono‐Nutrition Influence on Energy Expenditure and Bodyweight"
- Obesity:"The Human Circadian System Has a Dominating Role in Causing the Morning/Evening Difference in Early Diet-Induced Thermogenesis"
- NCBI: "Physiology, Glucose Metabolism"
- NIH: "Low Blood Glucose (Hypoglycemia)"
- Nutrients: "The Impact of Time of Day on Energy Expenditure: Implications for Long-Term Energy Balance"
- Dietary Guidelines for Americans
- Nutrients: "The Health Impact of Nighttime Eating: Old and New Perspectives"