Want to make breakfast the healthiest meal of your day?
Consider making breakfast the biggest meal of your day — while also including more fruits, vegetables, nuts, beans and other fiber-rich plant foods.
That’s according to the findings of a small but striking new study that compared what happened when people followed diets that were high in either protein or fiber. On both diets, participants ate a large breakfast and a small dinner — the exact opposite of how people typically eat in the United States and many other countries, where dinner is usually the largest meal of the day and breakfast the smallest.
The study, which was published in the British Journal of Nutrition, found that both the high-protein and high-fiber diets provided benefits. People experienced more satiety on the high-protein diet. But eating more fiber led to more weight loss. (All the participants were overweight or obese.) It also boosted their gut microbiomes, leading to an increase in intestinal microbes that have been linked to better gut and metabolic health.
The findings add to a growing body of research known as chrononutrition that looks at how the timing and size of our meals throughout the day affect our health. One of the most consistent findings from this area of research is that eating a big breakfast, a modest lunch and a small dinner may be better for your health.
Aligning your meals with your biological clock
Researchers say that eating your biggest meal in the morning aligns with the body’s 24-hour biological clock, or circadian rhythm, which governs everything from our sleep-wake cycles to daily fluctuations in our hormone levels and body temperature. That’s because our bodies are primed to digest food early in the day, while in the evening our metabolisms wind down as our bodies prepare for sleep.
Studies show that your body’s ability to manage blood sugar peaks in the morning and declines throughout the day, meaning our bodies are better able to metabolize carbs and other calories in the morning. Scientists have also found that our blood sugar control is directly impaired by melatonin, the hormone that our bodies secrete at night to signal to our brains that it’s time to go to bed.
Melatonin causes your pancreas to secrete less insulin while simultaneously making your fat tissue less able to absorb glucose from your bloodstream, said Marta Garaulet, a professor of physiology and nutrition at the University of Murcia in Spain, who was not involved in the new study. “Melatonin gives your body the signal that you should rest, and you shouldn’t eat,” she added.
These and other physiological changes throughout the day mean that a meal that’s consumed at 8 a.m. can have very different metabolic effects than the same meal consumed at 8 p.m.
In one randomized trial, scientists looked at what happened when they recruited a group of overweight women with metabolic syndrome and split them into two groups. Both groups were assigned to follow a low-calorie diet for 12 weeks. But one group routinely ate a large breakfast, a modest lunch and a small dinner. The other group did the reverse: They routinely ate a small breakfast, a modest lunch and a big dinner.
The scientists found that the women who consistently ate a large breakfast and a small dinner lost more weight, experienced less hunger and had greater reductions in their waist circumferences. They also had greater improvements in their blood sugar, insulin levels and other markers of metabolic health.
In another study published in the journal Obesity Reviews, scientists looked at data from nine rigorous clinical trials involving 485 adults. They found that people who were assigned to follow diets where they ate most of their calories early in the day lost more weight than people who ate most of their calories later in the day. They also had greater improvements in their blood sugar, cholesterol levels and insulin sensitivity, a marker of diabetes risk.
The effects of protein vs. fiber
Studies suggest that eating a hearty breakfast and a relatively small dinner can promote satiety and produce other health benefits, said Alexandra M. Johnstone, an author of the new study and a professor of human nutrition at the University of Aberdeen in Scotland. But relatively little was known about the effects of different meal compositions in the morning.
Johnstone said she and her colleagues wanted to look at the effects of a high-fiber breakfast in particular because most people in Britain — and in the United States and other developed countries — fall far short of the long-standing recommendation to eat about 30 grams of fiber daily.
“I’ve studied high-protein diets for many years,” she added. “I’m fascinated by how protein controls appetite and can be useful in many ways. But eating fiber is so important, and in the U.K. we have a fiber gap.”
For the study, Johnstone and her colleagues recruited 19 healthy adults and put them on two separate, strict diets for 28 days at a time. The participants had all their meals provided to them for each month-long diet, and they were tracked closely throughout the study. They consumed about 45 percent of their daily calories at breakfast, 35 percent of their daily calories at lunch and just 20 percent of their daily calories at dinner.
The high-fiber diet provided the equivalent of 30 grams of daily fiber for a roughly 2,000 calorie diet. The high-protein diet provided half that amount of daily fiber, and protein made up about 30 percent of daily calories.
On the high-protein diet, the participants ate things such as scrambled eggs, omelets, hard-boiled eggs, sausages, turkey bacon, toast, fruit smoothies and cereal for breakfast. For lunches and dinners, they ate foods such as chicken salad, tuna salad, roast beef sandwiches, turkey chili, chicken curry, and chicken with pasta and vegetables.
On the high-fiber diet, the participants ate a lot more plant foods. For breakfast they had things like whole-grain cereal, oatmeal with mixed seeds and raisins, muesli, bean frittatas, zucchini muffins, beans on toast and fruit smoothies. Lunches and dinners consisted of foods such as lentil soup, salads with barbecue chicken, hummus, chicken curry, breaded fish, brown rice, beans, vegetables, whole-grain bread and sliced fruit.
Less weight, healthier gut
On both diets, the participants saw improvements in their cardiometabolic health, such as reductions in their blood pressure, insulin and blood sugar levels.
On the high-protein diet, they reported feeling less hungry and more satiated. This was not entirely surprising because previous studies have shown that eating a lot of protein tends to promote satiety. But despite this, the participants lost slightly more weight when they ate a big breakfast combined with more daily fiber. They lost about 11 pounds on the high-fiber diet, compared with about 8½ pounds on the high-protein diet.
The researchers analyzed stool samples to see how the diets affected gut health. They found that on the high-fiber diet, the participants had more microbial diversity — which studies have linked to better metabolic health — and a “superior” gut microbiota profile. This included a greater abundance of beneficial gut microbes that produce butyrate and other short-chain fatty acids — special compounds that have been shown to reduce inflammation, boost cardiovascular health and help protect against colon cancer.
Johnstone said that whether you decide to eat more protein or fiber should depend on your health goals. If you experience hunger and cravings throughout the day, then eating more protein could be your best option. But if you are more concerned with improving your gut and metabolic health, then it might be better to eat a higher-fiber diet.
Here are some things to keep in mind:
- Studies suggest that having a big breakfast is generally better for your overall health than eating a big dinner. If you’re able, try eating more of your daily calories in the morning or afternoon. If you’re not usually hungry in the morning, consider having something light for breakfast followed by a large lunch and a modest dinner.
- Try to finish dinner at least three hours before bedtime. This will give your body time to digest and metabolize your meal before melatonin levels rise and peak, Garaulet said. She also recommends a nightly fast — the time between your last meal of the day and your breakfast the next morning — of about 12 hours.
- To increase the amount of fiber in your breakfast, try adding foods such as oatmeal, muesli, nuts, seeds, beans, fruits, veggies and whole grains. A high-fiber breakfast might be something like a bowl of plain Greek yogurt with berries, nuts, chia seeds and oats mixed in, along with a slice of toasted whole-grain bread with almond butter. You could also take psyllium husk, a type of fiber that can be consumed as a capsule or as a powder dissolved in water. Some people even mix it in their morning coffee.
- If you want to eat a higher-protein diet, consider eating things such as cottage cheese, scrambled eggs, breakfast burritos, chicken sausages, turkey bacon and protein smoothies for breakfast. For more ideas, read our article on healthy high-protein meals recommended by dietitians.
Do you have a question about healthy eating? Email [email protected], and we may answer your question in a future column.
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