In a previous article, Which meal should you skip for weight loss?, I discussed the findings of several studies that have examined the effects of meal timing on weight loss, metabolic rate, hunger and appetite. (Spoiler alert: eating the bulk of your calories at breakfast and lunch, and eating dinner early or skipping it altogether, is the best strategy for losing weight without deliberately restricting your food intake or suffering hunger pains.)
Newly published research has contributed to our understanding of how the timing of meals impacts our metabolism and either helps or hinders weight loss.
The title of the study is a bit of a give-away: Eating breakfast and avoiding late-evening snacking sustains lipid oxidation. ‘Lipid oxidation’ is fancy science-speak for fat burning, the holy grail of everyone who is aiming to lose weight or avoid gaining it.
Whereas many previous studies have mostly examined the effects of meal timing on the metabolism of young and middle-aged adults, the researchers who conducted this study deliberately recruited people aged 50+, reasoning that older adults “are more representative of populations at risk for metabolic disorders in many developed countries than are young and healthy adults.”
Their study subjects were confined to a metabolic chamber (a sealed room that allows metabolic rate to be precisely measured) for 2 separate 56-hour periods (that is, 2 1/3 days).
On one occasion, they were fed breakfast between 8 and 9 am, lunch from 12:30–1:30 pm, and dinner from 5:45–6:15 pm, after which they ate nothing until the following morning.
On the other occasion, they had only a cup of black, unsweetened tea or coffee at 8 am, then lunch and dinner at the same times as above, and a snack at 10 pm.
The lunch and dinner meals were identical on both occasions, and the same 700 calorie meal was served for breakfast as for the late night snack.
(You can see the meals the participants were fed here; be prepared to be horrified.)
In other words, participants ate exactly the same foods, with the same amount of calories, fat, protein and carbohydrate, during each of their study sessions.
They also slept during the same times of day (lights were turned off at 11 pm and back on again at 7 am), and both had the same duration of overnight fast (roughly 14 hours).
They also did the same amount of physical activity on both occasions – a light 20 minute stroll at 3 pm.
The only difference was whether they ate breakfast or a late-night snack.
And it turned out that this difference in meal timing made a substantial difference to how much fat participants burned in their sleep.
During the day, our bodies mostly use glucose as an energy source, but at night we switch to burning fat as our primary fuel. Just because you’re asleep doesn’t mean that your body is idle – all sorts of repair and maintenance tasks take place overnight, and your brain is still busy processing information even when you can’t consciously register it!
Once the fat from our last meal that’s still circulating in our bloodstreams has been taken up, our body fat stores – particularly the visceral fat that’s stored deep in our abdominal cavity – are broken down to ensure a constant supply of energy to all those energy-hungry cells.
But eating late at night delays the switch from burning primarily carbohydrate to burning mostly fat, and that means that less of your body fat stores will be used to keep your body running overnight.
How much less? On average, participants burned 15 grams less fat on the nights after they skipped breakfast and ate a late-night snack than when they ate breakfast and finished their day’s food intake by around 6 pm.
15 g may not seem all that exciting to you if you’re quite overweight, but remember that this increased fat burning occurred after just one day of an altered meal pattern, and the participants were fed very unhealthy foods including bagels with cream cheese, hamburgers and fries, and roast beef with white bread rolls and butter.
If this amount of fat was lost from your visceral stores every night, by the end of 6 months you would have lost over 2.7 kg of fat from around your midsection – the most dangerous place to carry fat.
Just think what you could do if you combined this altered meal timing with a healthy wholefood plant-based diet!
Actually, findings from the Adventist Health Study 2 have already provided hints about what you could expect. Seventh Day Adventists (SDA) throughout the world have a proud record of being far healthier and longer-lived than their non-SDA neighbours, with substantially higher life expectancy and reduced rates of cardiovascular disease, type 2 diabetes and certain cancers.
The religious beliefs of SDAs place a heavy emphasis on healthy living, including eating a more plant-centric diet (over half of US and Canadian SDAs are either vegan, vegetarian, pescatarian or semi-vegetarian).
Even among this health-conscious population, those who ate 3 or more meals per day were found to gain weight over an average follow-up period of 7.5 years, while those who ate only 1-2 meals per day were far more successful at maintaining a healthy weight.
The bottom line: The evidence that a meal pattern consisting of a large breakfast, middling-sized lunch and small dinner, eaten as early as possible, is best for weight loss (specifically, a reduction in body fat and especially in visceral fat) continues to mount.
Switching to such an eating pattern entails some logistical challenges for most people, but the benefits are so compelling that it’s worth rearranging your daily activities to make it possible, even if you don’t stick to it 7 days per week.
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