What Are the Best Times to Eat for Weight Loss?
While we know that what we eat impacts our weight, we rarely discuss how the timing of our food intake affects our weight. Many studies have now shown that when you eat can impact your weight and overall health.
Many studies have now shown that, yes, when you consume food can impact your weight and overall health. The American Heart Association has even endorsed the principle that the timing of meals may impact your risk for heart disease, high cholesterol and blood pressure. There are a few theories on what factors come into play with meal timing and what are best times to eat to maintain a healthy weight.
The human body likes a regular schedule. It’s part of your natural biorhythm–your body’s daily cycle. Every 3 to 5 hours, it is time to eat again, to replenish calories and refuel your system. Eating meals at nearly the same time every day can help to maintain a healthy weight and ward off weight gain. Some studies have found that people who eat consistent meals–both time of day and number of meals per day–had better cholesterol and insulin levels. They are also less likely to be obese. These papers, published by the Proceedings of the Nutrition Society, found that irregular meals can set you up for obesity, type 2 diabetes, and high blood pressure no matter how many calories you actually eat.
“We found that adults consuming calories during regular meals—at similar times from one day to [the] next—were less obese than people who have irregular meals, despite consuming more calories overall,” says Gerda Pot, PhD, a visiting lecturer in the Diabetes and Nutritional Sciences Division at King’s College London who worked on both papers.
Eating at strange times can throw off our circadian rhythms. It’s thought that the lack of synchronicity may alterf how we metabolize food and store fat. These metabolic processes include appetite, digestion, and the metabolism of fat, cholesterol, and glucose. Our metabolic processes follow a pattern that repeats every 24 hours. If you disrupt that cycle, you put yourself at risk for weight gain and other health issues.
A study by the University of Murcia in Spain found that people eating their largest meal of the day before 3pm lost more weight than those eating their largest meal after 3pm. (In Mediterranean culture the main meal is lunch.) In a 20 week study, the researchers had 2 groups: one group ate their mid-day meals before 3pm and the second group ate it after 3pm. They consumed similar calories, slept a similar number of hours and exercised roughly the same amount. The lunch time meals comprised about 40% of the caloric intake for the day. The group eating their lunch after 3pm, lost less weight and had a slower rate of weight loss than the group eating lunch early in the day. The conclusion is that time of day should be considered in a weight loss plan.
Another study looked at restricting your caloric intake to between the hours of 8am and 2pm. The study done by the Department of Nutrition Sciences at University of Alabama-Birmingham proposes that eating in a more limited window during the day aids weight loss and promotes calorie expenditure. Half the participants ate anywhere during the time period of 8am to 8pm. The other half ate only during the shortened window, therefore eating dinner much like in the University of Murcia study, before 2pm. Both groups ate the same caloric intake. The group eating only earlier in the day experienced more even hunger levels throughout the day and higher metabolic flexibility, both of which can help in weight loss. Metabolic flexibility is the ability of the human body to switch between carbohydrate burning mode and fat burning mode. Higher metabolic flexibility leads to burning more fat at night. In addition to diminished swings in hunger, the early eating participants were not hungrier on average despite having to fast for 18 hours every day. Researchers posited that these participants’ bodies had registered that they had already consumed enough calories for the day, therefore minimizing the need for additional hunger cues. For people who eat dinner later, the body desires more fuel, and therefore hunger cravings occur to drive the acquisition of those calories. Research on fasting has demonstrated that the hunger hormone, ghrelin, has a learned response; it increases at times when you typically eat. In a study by Natalucci and colleagues, individuals fasted for 33 hours and had their ghrelin levels measured every 20 minutes during the fast. Ghrelin levels increased at normal times for breakfast, lunch and dinner, but decreased after the mealtime, even when food was not consumed. The hunger hormone levels did not progressively increase during the fast, but stayed almost flat between mealtimes. Though not measured in the University of Alabama study, the adaptive capacity of ghrelin may have played a role in the diminished hunger swings. While the initial study of eating before 2:00 pm was small, researchers are optimistic that eating earlier can aid weight loss.
Eating more at breakfast and less later in the day can have potential health benefits and promote weight loss. We are programmed to burn more calories/energy early in the day. We metabolise meals in the first part of the day better than those later in the day. A 12 week study done by the Obesity Society studied the impact of a weight loss diet with high caloric intake during breakfast to a diet plan with high caloric intake at dinner. The breakfast group ate 700 calories at breakfast, 500 calories at lunch and only 200 calories at dinner, while the dinner group at the exact opposite with 200 calories at breakfast, 500 at lunch and 700 at dinner. The breakfast group lost more weight and saw a great reduction in waist circumference. They also experienced higher overall health benefits including a decreased risk of type 2 diabetes and cardiovascular disease.
Eating a larger breakfast gives our bodies the fuel they need for the hours in which we are most active. A slightly smaller lunch keeps us energized throughout the afternoon. Tapering to a small dinner at night, begins to move our bodies into a fasting mode. We also are typically less active after eating in the evening and not burning as many calories as we do throughout the day. Reorienting our caloric intake to the parts of the days where we are most active could be an effective part of a weight loss program.
So, is breakfast the most important meal of the day? It’s possible. It’s long been believed that eating breakfast aids in healthy weight maintenance and leads to more energy, better blood sugar regulation and higher energy levels. Skipping breakfast is linked to higher levels of obesity. People who skip breakfast are also more likely to snack impulsively and have a higher fat intake. A study by the Psychology Department at Vanderbuilt University studied two groups: one that ate breakfast and 2 more meals throughout the day, and another group that only ate 2 meals a day. Snacks were restricted. Even though they consumed a different number of meals, they consumed the same amount of calories per day. Weight loss was seen in both groups, but those who ate breakfast lost more weight.
A similar study done by The School of Public Health at Loma Linda University found that participants who ate 3 meals per day, but didn’t snack had lower BMIs. The study tracked 50,000 adult participants for seven years. Eating breakfast, eating more calories early in the day and fasting longer overnight led to lower BMIs, the researchers concluded.
But, some studies have found opposing results. A study from the Department of Health Behavior found that whether participants ate breakfast or not did not seem to have much correlation to weight loss. In a 16 week study, two groups ate the same number of calories per day, but one group ate breakfast and one group did not. There was no significant effect on weight loss in either group. There seems to be no decisive conclusion on breakfast.
It may be that eating breakfast is very important for a significant number of people and less important for other individuals. For those who skip breakfast and find themselves overeating at lunch and later in the day, adding breakfast may have significant benefits. Individuals who have a natural later eating-style, missing breakfast may not impact food intake later in the day or interfere with weight loss.
The idea that those who eat more calories late at night are more likely to gain weight is not a new concept. Late eaters tend to eat more calories, are less likely to lose weight, and are at a higher risk for diabetes. A University of Pennsylvania study by the researchers at the Perelman School of Medicine found that late night eaters had higher insulin and cholesterol levels, increased risk of heart disease, and poor fat metabolism.
So why does late night eating lead to weight gain? Because our bodies respond differently to calories consumed at different times of day. Satchidananda Panda, a molecular biologist at the Salk Institute for Biological Studies, has found that mice who only eat during their active times of day are drastically healthier and thinner than mice who eat randomly throughout a day. Why? Because our bodies process calories more efficiently during day time hours.
A recent study published in The American Journal of Clinical Nutrition examined the impact on body composition of eating closer to one’s biological night. The rise of melatonin levels in the blood signal the onset of our circadian rhythm night cycle. The onset of the night cycle varies from person to person, therefore night eating may occur during one’s day or night cycle. The researchers found that individuals who ate most of their calories closer to their nighttime release of melatonin (within 1.1 hours) had higher levels of body fat when compared to lean participants, even though there was no significant difference between the groups as to the clock time of food consumption. This correlation between a higher percent body fat and eating during one’s night cycle is independent of food type, calories consumed and activity level.
Another study done by researchers at UCLA School of Medicine has found that late night eating could be linked to other health problems – prominently memory issues upon waking and long term memory loss. In tests conducted on mice, the mice were fed regularly in a six hour window during the day, and their ability to remember an object was observed. Next, they fed them only during a six hour window in their normal sleeping hours, then tested their memories. After eating late, mice struggled to recall the object and over time, it was discovered that their long term memory was dramatically impaired. Both learning and memory can be impacted.
“Modern schedules can lead us to eat around the clock so it is important to understand how the timing of food can impact cogitation,” said the study’s co-author Christopher Colwell, a psychiatry professor at UCLA.
There are many clear signs now that eating after dark negatively impacts our circadian rhythm, leading us to be more likely to gain weight and have a potential variety of other health issues.
There is clear evidence that when we eat can impact our weight. Being more mindful of our snacking patterns and when we schedule our meals can lead to better weight management and improved overall health. When putting together a weight loss plan, take into consideration when you eat. Note if you are eating very late in the evenings and if evening snacking is a problem for you. Consider shifting your dinner time forward, if possible, to allow your body a longer time to fast. Take the time to eat a well rounded breakfast in the morning as it is most likely going to set the day up for higher success. Whenever possible, try to eat your meals around the same time of day. Busy and shifting schedules can certainly make this challenging, but with a little effort, you can stay in sync with your body’s natural rhythms and feel and look the better for it.