There’s an old adage: “Breakfast like a king, lunch like a prince and dinner like a pauper,” and it appears to have some truth. Timing of meals may play a part in controlling weight and health. There is emerging research to say that eating too much at night may not be good for health; however, there is not much research to show exactly which meal (breakfast or lunch) should be the heaviest.
Consuming more than a third of daily energy intake at an evening meal doubled the risk of obesity compared to consuming more than a third of energy intake before noon. Similarly, another study in which subjects were assigned to consume a larger proportion of their energy at breakfast lost more weight than those who consumed a majority of their energy at dinner. Having lunch later than 3pm also resulted in less weight loss and more insulin resistance (regardless of calorie intake). The reasons for this phenomenon is uncertain, although a study showed that eating lunch at a later time (4.30pm) than earlier (1pm) caused lower metabolic rate and lower carbohydrate use. These data suggest that weight control may be more effective if a larger proportion of total daily calories is taken in the morning rather than later in the day.
Additionally, there have been some studies (both animal and preliminary human studies) that show time-restricted fasting (restricting any calories from food and beverages) for 12-14 hours overnight may have some benefits for weight loss, reduce risk factors related to diabetes, cancer and heart disease; and that this can occur regardless of the total calories consumed. But this is true only when intake is restricted to earlier in the day rather than late at night. Unfortunately, humans are not mice, and even in human studies it is incredibly difficult to tease out potential benefits of a diet with other factors.
Hence, larger scale human studies are required to confirm these results, and especially to compare the effectiveness of diet controlling time/frequency of meals compared with other calorie-restricted diets which have stronger evidence.
I heard somewhere that lunch being the heaviest meal helps with weight loss. Is this true?
There’s an article by PopSugar that says that lunch should be the heaviest meal. This is based on a research study published this year. PopSugar’s article explains the differences between the two groups, with those having a heavier dinner (dinner group) losing less weight than those having heavier lunch (lunch group). Let’s delve deeper into the study design to show that while it’s promising results, the evidence is not strong enough to recommend this specific rigid diet plan.
Something that wasn’t considered thoroughly in the study was the total calorie reduction between the two groups. Although it was considered not ‘statistically significantly different’, comparing the beginning of the study to the end (12 weeks later), the lunch group ate an average of 383 calories less each day. Compared to 332 calorie less for the dinner group.
This means that the lunch group’s reduction in calories was 51 calories more per day compared to the dinner group. 51 calories x 7 days x 12 weeks = 4,284 calories over the whole intervention (in terms of the calories reduced in the dinner group vs lunch group on average). The total carbohydrate, fat and protein intake is also a bit higher in the dinner group at Week 12 (although not ‘statistically significant’).
Considering 7,700 calories is approximately the amount you need to cut down to lose 1kg body fat, the fact that the lunch group had a greater total calorie reduction of roughly 4,284 over the whole intervention does translate to almost 0.6 kg reduction (that’s about 1.3 pounds).
That does account for some of the approximate 3.2 pounds extra weight loss from the lunch group. So perhaps it was not purely due to the fact that the participants lost weight because of the timing, but it might be also to do with the total calories being less each day when they ate a heavier lunch.
Why could eating a heavier lunch mean slightly lower calorie intake overall? It’s all speculation, but it could be because those who were told to have heavier lunches, didn’t have a lot of time to prepare large elaborate lunches in the first place (as they could be working and busy to prepare or spend much time eating. After all, you’re more likely to be grabbing a quick sandwich or soup at lunch than wanting to gorge on a big bowl of pasta at a nice restaurant when you have a meeting scheduled soon!). Then when they go home, they realise that the dinner is meant to be only 20% of their total calorie intake, and so they consciously reduce their dinner.
Whereas those who were assigned the dinner heavy group, could be eating similar lunches as their usual (e.g. lighter meals like sandwiches), and then perhaps when they reach home, they know that they can ‘gorge’ on 50% of their calorie intake, and have the time and effort to prepare something nice or go out and eat something fancy or indulgent.
And when are you more likely to mindlessly eat unhealthy snacks? When you’re busy at work, or at home after work while watching TV? For most people, it would be the latter. If you know you’re supposed to eat ‘more at night’ (i.e. the dinner group), you’d be more inclined to eat more midnight munchies, than somebody who knows they shouldn’t be eating too much at night (i.e. the lunch group). While the study said that the calories and nutrient composition of the two groups were similar during the intervention, there is research that shows underreporting of eating in overweight people, especially for snacks. So in effect, there could potentially be an even greater calorie reduction difference between the two groups than reported.
Another factor to consider is that when people are given the option to eat more at night, they probably will spend more time eating (or possibly preparing food) too, which leaves less time for physical activity (since most people wouldn’t do exercise at work in the daytime). Whereas those who were assigned ‘lunch group’ would have spent less time on preparing or eating a large meal at night after work, and had more chances to do physical activity. Hence, higher chance of burning calories and losing weight.
The only way to know for sure whether the difference in weight was due purely to the timing of the meals (rather than the total calorie input and output), is to provide all meals to the people, make sure they do not eat anything else, and make sure they are doing the same levels of activity. This is obviously not what the study did, so it is erroneous to say that the timing of the meals is the definite reason.
There are other issues with the study too (as with all studies), such as the fact that it was only done on overweight women age 18-45 and a small sample size of just 80 people in the UK. It therefore cannot be said that the same is necessarily true for Asians living in Singapore, for males, or for people older than this age. 80 people is also too small to consider as ground-breaking enough to change nutritional guidelines.
It also only lasted 12 weeks, so we don’t know exactly how long-term this effect might last. They also never had a ‘breakfast-heavy’ group, meaning we don’t know whether breakfast being the heaviest meal could in fact be even better. There’s even research that says having a ‘light lunch’ can help with weight loss. Bearing all these issues in mind, it is not prudent to change your diet drastically to focus solely on lunch just because of this one research study.
Ok, so lunch may not necessarily be the best to have your heaviest meal. But, why could it be better to eat more earlier in the day, than more food at night?
Our body’s metabolic rate is slightly slower at night as we are not using up energy for moving and so forth, but it is still using up energy from food and our digestive system is still working then. There may be health benefits to have the majority of your calories in daytime rather than at night. Research is still lacking for exactly why, but it may involve complex mechanisms of appetite regulation, metabolism and circadian rhythm. Our body seems to deal with calories better earlier in the day. The greatest insulin sensitivity happens early in the morning which decreases as the day goes on, which could lead to higher blood sugar levels later in the day. Our blood triglycerides (blood fats) are also higher at night, and they also remain elevated for longer in response to a meal compared to when it is eaten in the day. Moreover, avoiding a big late-night meal right before bedtime may be for practical reasons too, as it may give you a boost of energy (making it difficult to sleep) or cause reflux.
While all meals of the day are important in their own ways, research suggests a role for regular breakfast consumption in maintaining a healthy weight. Currently there isn’t enough research to recommend any strict timing for meals, cut-off time to eat or a definite proportion of calories at each meal.
Wouldn’t 600 calories for lunch cause a food coma and therefore, unproductive hours after lunch in the office?
The PopSugar article suggests to aim for 40% calories at lunch, which is around 600 calories of a typical 1,500 calorie diet for weight loss. Many Asians, especially those with a smaller frame and having a sedentary lifestyle, may actually need 1,200 or even less calories per day for weight loss. This means around 480 calories at lunch. A meal around 480-600 calories is typical of a usual hawker centre meal with balanced nutrients (e.g. mixed veg rice with 2 veg + 1 protein; or a fish slice noodle soup).
However, my personal mantra is not to follow ‘rules’ or calorie count, but instead to listen to your own body’s cues about fullness. If you are already feeling satisfied with your meal, you shouldn’t have to force yourself to eat a set amount. There is hardly any strong enough evidence to be setting an exact percentage of calories based on just one research study. Instead, this could be viewed more as a rough guideline to prevent overeating at dinner or night snacks.
A ‘food coma’ is caused by the fact that more of our blood goes to our gut when digesting our meal, leaving less blood for the rest of the body. Because of this, some people might feel a bit “light-headed” or tired. Scientists have shown that meals high in high GI (glycemic index) carbohydrates (like white rice or white bread) cause an increase in insulin in the blood. Insulin allows the entry of tryptophan (a type of amino acid) into the brain, which can make us sleepy. High-fat foods also send signals to the brains to focus our energy on digesting (rather than energy for the rest of the body). Consuming a high-protein meal, on the other hand, will cause a lot of other amino acids to enter the brain and will probably have a stimulant effect instead of drowsiness.
The important take-home message is that it’s important to have a well-balanced meal that’s not too high in fat, choose high-fibre carbs (like brown rice or wholemeal bread), include protein, vegetables and fruits in your meal, and don’t overeat (just because of a ‘rule’ that somebody suggested online without considering your individual needs), but instead listen to your own body. If you follow these guidelines, having a ‘heavier’ lunch is unlikely to cause a food coma.
Ultimately the total calories and overall healthfulness of your food choices have a much greater impact on your health and weight loss than the timing of your heaviest meal. Everybody has different lifestyle habits, work cycles, eating preferences, and cultural backgrounds, that may make one meal of the day slightly heavier than another, and that’s ok. It is best to stick to a healthy eating plan that you can follow for life, not one that is impractical for you. If you eat three wholesome, balanced and healthy meals, low in fat and sugar, and chockful of lean protein and fibre, it is likely to help with weight loss; regardless of how you spread out the calories. In contrast, if you eat lots of processed fast food, sugary drinks and have a high-fat, low-fibre diet, it will be hard for you to lose weight regardless of which meal you eat more calories.
Nevertheless, the American Dietetic Association states that total calorie intake should be spread throughout the day with 4-5 meals (including breakfast), and consuming more energy throughout the day may be better to more energy at evening consumption. Based on the preliminary evidence, it’s worth trying to stick to regular meals at reasonable timings and to avoid having a super heavy dinner or supper. To simplify, it is not known whether breakfast or lunch should be heaviest, but one thing is for sure, it is best not to stuff in most of your calories at night.
Contributed by Bonnie Lau, an Australian-trained Accredited Practising Dietitian.
Photo credits: Shutterstock
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