Weight loss can be tied to when, not just what, you eat

Story highlights

  • Circadian-synced diet has been linked to weight loss
  • Experts recommend not skipping meals or eating too few calories earlier in the day

(CNN)If you are trying to lose weight and otherwise improve your health, you may already be mindful about what you eat during the day.

You might skip breakfast. At lunch, you may opt for a salad with lots of veggies, no croutons and low-fat dressing -- on the side, of course.
Then, three o'clock hits.
    You're incredibly hungry and craving candy, sweets or chips. You finally cave, eating a candy bar or other treat.
    By 6 p.m., you're tearing the kitchen apart, snacking on anything you see.
    Despite your best efforts at cutting carbs at meals, you give in to a large helping of pasta or pizza. And then another. But you're still not satisfied. Dessert is calling, and you want something sweet, again. A scoop or two of ice cream satisfies you for the moment, but you continue to graze into the night until finally, you're so tired, you crash into bed.
    So what is the cause of all of this diet drama that keeps occurring, almost according to schedule?
    "I started noticing a common pattern where my patients were so good with restricting their calories during the day, but in the late afternoon and evening, they fell apart," said Tamara Duker Freuman, a nutritionist who has helped hundreds of people lose weight over the past decade on a meal-timing based plan she describes as the "circadian-synced diet."
    "It was the ongoing grazing into the night. ... That's what kept undermining them. They often thought they were binge eaters ... but in reality, they were just really hungry.
    "If they just ate a little more at breakfast and lunch, if they just added a few hundred extra calories in the morning, they would get their eating under control and lose weight," she said.

    The research on front-loading food

    It's true that over-consuming calories at any time of day will result in weight gain. But skipping meals or eating too few calories earlier in the day appears to stack the odds against us. The result: Weight loss is hard to come by. In fact, more and more research points to the fact that when you front-load your calories instead, you have a much better chance of shedding pounds.
    "What we have seen is that people on diets with the same number of calories who front-load calories to the earlier part of the day fare better in terms of subjective and objective measures of satiety," Freuman said. "They feel more satiated in evening, and there are actually differences in their hunger and satiety hormones ... and this seems to contribute to weight loss success."
    One study involving 420 overweight and obese participants divided individuals into two groups: early eaters and late eaters, based on the timing of their lunch (i.e. before or after 3 p.m.). The late lunch eaters also ate lower-calorie breakfasts or skipped breakfast more often than early eaters.
    At the end of the 20-week study period, the late eaters lost less weight compared with the earlier eaters (17 vs. 22 pounds on average, respectively) and lost their weight more slowly, despite the fact that both groups ate approximately 1,400 calories per day and consumed similar amounts of fat, protein and carbohydrates.
    Another study followed two groups of overweight women with metabolic syndrome on identical 1,400-calorie weight loss diets for 12 weeks. The only difference between the groups was that their calories were distributed differently throughout the day: Both groups consumed 500 calories at lunch, but one group consumed 700 calories for breakfast and a 200-calorie dinner (the "big breakfast" group), while the other group ate 200 calories at breakfast and 700 calories at dinner (the "big dinner" group).
    The nutrient content of the meals was exactly the same for both groups, the only difference being that the breakfast and dinner meals were swapped. After 12 weeks, the big breakfast group lost about 2½ times more weight than big dinner group (8.7 pounds for big breakfast group vs. 3.6 pounds for big dinner group) and lost over 4 more inches around their waist.
    The big breakfast group experienced a 33% drop in triglyceride levels -- a marker associated with heart disease risk -- while the group that ate the higher-calorie dinner experienced a 14.6% increase. The bigger breakfast group also experienced greater reductions in fasting glucose, insulin and insulin resistance scores, all of which indicate decreased risk for type 2 diabetes, according to the study's authors.
    So front-loading calories and carbohydrates is not only favorable in terms of weight loss, it had beneficial effects on other indicators of overall health, including decreased risk for type 2 diabetes and cardiovascular disease.
    That second study "opened my eyes," Freuman said. "It wasn't just that people were less hungry and eating less at night, but it pointed to the fact that there might be some sort of underlying metabolic magic going on, where the timing of calories and carbs mattered more than the total amount of calories and carbs eaten in a day. It helped me understand what I was intuitively seeing in my patients."

    Circadian rhythms: the 'metabolic magic'

    More and more research is suggesting that when you eat may be just as important as what you eat. And it is very closely tied to the complex science of circadian rhythms.
    According to the National Institute of General Medical Sciences, circadian rhythms are physical, mental and behavioral changes that follow a roughly 24-hour cycle, responding primarily to light and darkness in an organism's environment.
    Circadian rhythms are driven by biological clocks inside our bodies. The brain has a master biological clock, influenced mainly by light, which tells "peripheral" clocks in the muscles and organs what time of day it is. Because of these clocks, many of the metabolic processes that take place inside us operate at different rates over the course of a 24-hour period.
    "Because of circadian rhythms, there are variations in certain hormone levels, enzyme levels and glucose transporters at different parts of the day, which differentially affect how calories, carbohydrates and fat are metabolized," said Freuman, who presented case studies of patients who improved their weight and health by eating in sync with circadian rhythms at the New York State Academy of Nutrition and Dietetics annual meeting in May 2016.
    Circadian rhythms can help explain why eating late at night increases the likelihood of weight gain and decreases the rate at which we lose weight, compared with eating earlier in the day.
    For example, research suggests that the calories we burn from digesting, absorbing and metabolizing the nutrients in the food we eat -- known as diet-induced thermogenesis -- is influenced by our circadian system and is lower at 8 p.m. than 8 a.m., according to Frank A.J.L. Scheer, director of the Medical Chronobiology Program in the Division of Sleep and Circadian Disorders at Brigham and Women's Hospital in Boston.
    Other metabolic processes involving insulin sensitivity and fat storage also operate according to circadian rhythms and can greatly influence the likelihood of weight gain or weight loss at different times of the day.
    "These different metabolic processes ebb and flow at different times of the day, and they play a role in how your body metabolizes food energy, which ultimately affects your weight, cholesterol levels and blood sugar control -- and so it has tremendous implications for what is considered optimal times for eating," Freuman said.

    Breakfast-skippers beware

    Circadian rhythms may help explain why breakfast skipping is associated with increased risk of weight gain, even among those who consume comparable amounts of calories in a day.
    "The link between breakfast skipping and obesity had once been thought to be due to overcompensation of calories at subsequent meals due to excess hunger ... but the research does not consistently show differences in total energy intake among breakfast-skippers," Freuman said.
    "Something else about skipping breakfast -- aside from potentially eating more calories later in the day -- must explain the greater risk of weight gain among breakfast skippers," she said. A more likely answer: Eating more calories in the later part of the day is out of sync with metabolic circadian rhythms.
    "We get less metabolically robust as we age," she explained. "So even if you've gotten away with skipping breakfast and eating out of sync in your 20s or 30s, it may eventually catch up with you."
    Night shift workers can also benefit from eating in sync with their circadian rhythms. They may modify meal timing to sync up with metabolic circadian rhythms by eating breakfast at the end of their workday, at 7 or 8 a.m., and then eating their heaviest meal when they wake up, about 3 or 4 p.m.
    Freuman discourages her night shift patients from eating during the night. "We don't want them eating many calories, so we'll have them sip on tea or have a Thermos of miso soup or, if need be, something small like an apple in order to minimize overnight calories.
    "Your metabolism is working in a certain way, whether you are awake or asleep -- so even if you are awake during most of the night, you still want to be eating most of your calories during daylight. Sleep has little to do with it," Freuman said.

    Tips for eating in sync with circadian rhythms

    So how do we eat in sync with our circadian rhythms? They key is to front-load your calories and carbs. Freuman suggests the following, which she advises to her patients:
    1. Don't skip breakfast
    Ideally, breakfast should be satiating enough to preclude the need for a midmorning snack, and it should have a minimum of 300 calories, according to Freuman. It should always include high-fiber carbohydrates, which are more slowly digested than refined carbs, and it should include protein, which helps keep hunger in check.
    Good breakfasts include a cup of cooked oatmeal with low-fat milk and a small handful of nuts, two slices of Ezekiel or whole-grain bread with mashed avocado and sliced tomato, or a two-egg omelet with veggies, fruit and a slice of whole-wheat toast.
    If you are not hungry when you wake up, you can defer breakfast for a few hours -- but it should not be skipped, according to Freuman.
    2. Have the "blue plate special" for lunch
    "Lunch should be like that blue plate special ... the main meal of the day," Freuman said.
    For a simple lunch strategy, Freuman suggests filling half of your plate with non-starchy vegetables and then dividing the second half into protein (like grilled fish or chicken) and slowly digested high-fiber carbohydrates (like beans or quinoa). "A salad with grilled chicken is fine, but try adding a baked sweet potato, a heaping scoop of chickpeas or even a thick, hearty lentil soup," she said.
    If you prefer a sandwich for lunch, pair it with fiber-rich vegetables. "A turkey sandwich is part of a good lunch, but it's not a whole lunch." Try adding butternut squash soup or carrots with hummus.
    Other good lunches that Freuman recommends include baked salmon with lentils and cooked green veggies or a Mexican quinoa bowl with quinoa, black beans, chicken, avocado and salsa, along with a pile of greens.
    The easiest way to plan for lunch may be to use last night's leftovers. "I cook dinner at home and bring in my leftovers for lunch the next day. When I get home from work, I'm not tearing the house apart."
    3. Pack a snack
    An afternoon snack may be necessary if lunch and dinner are more than five hours apart. However, it should be no more than 200 calories, and it should be high in protein and fiber. "This will prevent you from arriving at dinner feeling 'starving,' " Freuman said.
    Snacks that will satisfy include an apple with a tablespoon of peanut butter, grape tomatoes with string cheese, a hard-boiled egg or plain Greek yogurt with fruit.
    4. Go low-carb for dinner
    Dinner should be light and low in carbohydrates. "The more you can go low-carb for dinner, the more it will mitigate the effects of distorted calories at night," Freuman said.
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    Dinners might include fish and a cooked vegetable, lettuce-wrapped tacos or a turkey burger (minus the bun) and a salad with light dressing.
    "I'll make turkey meatballs for my kids, and I'll give them pasta too, but I'll have mine on a bed of spinach -- and the next day, I'll bring the pasta for lunch."
    And when dining out, Freuman suggests ordering two appetizers, like a salad and a shrimp cocktail or grilled calamari.