When you eat could be as crucial as what you eat

The old adage, “Breakfast like a king, lunch like a prince and dine like a pauper” has been around for years and is widely attributed to American nutritionist Adelle Davis, who wrote a number of nutrition books in the 1940s and 50s and became one of the most influential figures in diet and nutrition in the US – she pretty much was the godmother of nutrition in many ways.

But this isn’t about Adelle, it’s about one of her theories regarding nutritional timing. Do we burn calories equally throughout the day, or are they periods where the body starts to burn calories more slowly?

Last month, the BBC published an article based on research conducted by the University of Aberdeen suggesting that larger breakfasts and smaller dinners could help with weight control as eating earlier in the day suppresses appetite later.

The principle is based around nutritional timing which, in this case, suggests that eating with the natural biological rhythms of our body (known as Circadian rhythms) can help us manage our appetite much more efficiently. Eating late at night is a poor time to consume calories because our body rhythm is slowing down, preparing us to sleep. Whereas earlier in the day, the opposite is true.

The researchers used a system to measure how we utilise calories called “doubly-labelled water”, and discovered that whatever time we eat, we still burn calories at the same rate. So it might not be about our metabolism.

Eating larger meals earlier suppresses our appetite, so if we had a large breakfast, we often don’t want to eat quite so much at lunch or dinner. Other explanations involve the effect time of day has on our natural hormone and enzyme activity. Insulin, for example, has lower sensitivity in the evening than it does in the morning (1,2) and this can impact on how well balanced our blood sugar levels are.

What do other studies say?

In 2017, a systematic review was published that collected the findings from ten different studies that between them included over 6000 participants. They noted that obesity and onset of type 2 diabetes (which is often associated with obesity) was lower in people who ate most of their calories earlier in the day (3). A new term has arisen following this discovery, which describes obesity and obesity-related diabetes as “chronobiological diseases”, meaning that these conditions are associated with meal timing.

An earlier review looked at calorie intake and meal time among shift workers who typically consume their calories later in the day. It found that people who work night shifts compared to those who worked during the day did not consume any more calories which, the authors conclude, suggest that meal timing influences rates of obesity. Eating late at night appears to disrupt our natural body rhythm. (4).

This could partially explain why some people who diet and exercise are struggling to lose weight – are they consuming their calories at the wrong time? If people eat the same calories, but at different times of the day, then perhaps something else is at play than just how much we eat.

More recent studies found that when we eat has an impact on what goes on in our fat cells as well as our appetites. One US study (5) wanted to test why eating late contributes to weight gain. They noted that eating later had a significant and profound effect on the satiety hormones, which influence our drive to eat. Eating later suppresses the hormone that stops our drive to eat for up to 24 hours. It also changes mechanisms in fat cells that promote fat burning so that at a molecular level, fat cells turn on storage rather than usage.

In the same month, another study was published that found similar effects in mice and discovered the actual mechanisms that drive this (6).

Not everyone wants to eat breakfast, or feel they have time to do so. In this busy environment we’ve found ourselves in, getting up, having a shower and then commuting to work leaves little time for many of us to do much more than grab a coffee on the go and hope that keeps us going until lunch.

But since the pandemic, a good proportion of us have found ourselves working remotely, which has significantly cut down the commute. If this is you, then now is a great time to start new habits – such as eating breakfast that’s high in protein and dietary fibre. Between the two of them, these nutrients help suppress appetite and keep us feeling fuller for longer.

Protein can come from many sources such as milk (with cereal for example), yoghurt, eggs, fish, or meats. Plant-based sources are much easier to find these days such as coconut yoghurt, nuts and seeds (as nut butters, but choose the 100% nut varieties without added palm oil or salt), tofu-based “scrambled eggs”, and tahini spreads such as hummus or moutabal (baba ganoush in the US).

Good sources of dietary fibre are all plant-based and include nut butters, whole grain bread, avocado, fruits (not fruit juice or smoothies), oatmeal (porridge, overnight oats or muesli) or whole grain crackers.

For busy people, having something prepared the night before that they can grab quickly in the morning could be a real help. My go-to option is overnight oats. My first reaction to this was disdain as I did not like the texture of soaked fruits! I had tried Bircher muesli as it was fairly trendy a few years ago, but the oats to fruit ratio didn’t work for me.

When I switched to more oats, less fruit, I found it more palatable and kept my hunger at bay longer. I now top it with coconut yoghurt, a scattering of seeds, and some blueberries, sliced strawberries or other berries. This can be eaten straight from a sealable food storage box at my desk as I read emails and respond! It takes only a few minutes to prepare the night before and just grab from the fridge as I head out of the door.

There are so many ways to do overnight oats that it really is a portable breakfast that can be eaten anywhere, so long as you have a spoon to hand!

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