Richard Collins: Studying science and evolution to figure out dinnertime

Is it healthier to eat your main meal in the middle of the day? A study on mice may have some answers

The 'Sunday roast' and dinner in the middle of the day were traditions — but is it healthier to eat our main meal in the evening? A scientific study of different feeding regimes for mice has been published

Lunchtime was ‘dinnertime’ when I was a boy. Most mammies stayed at home and cooked. The daddies returned from work in the middle of the day. It was German, English, and Irish, custom.

During the 1960s, the package-tour and the jet aeroplane arrived. People of modest means could now afford to visit ‘the continent’, where France and Italy ruled the gastronomic roost. Our national inferiority complex kicked in; having the main meal in the evening became ‘chic’. Like the Cornish tin-miners with their ‘pasties’, we began taking flasks and sandwiches to work. The Sunday roast is the sole survivor of the old order.

Eating in the middle of the day may be more practical in organised living, but is it healthier? Research just published addresses this question — with regards to mice anyway.

Joseph Takahashi and colleagues at the Howard Hughes Medical Institute, subjected hundreds of laboratory mice to differing feeding regimes over a four-year period. By reducing their food intake, the research showed, the mice lived longer. A 30% ‘caloric restriction is sufficient to extend lifespan by 10%’. This result was expected: rats and primates, even insects, had increased longevity when subjected to similar regimes. Eating less, the health experts tell us, keeps the grim reaper at bay for longer.

But the mouse research suggests that it’s not just how much we eat, but when we eat, that’s important. When the rodents were fed at night, and not during the day, their life-expectancies increased; the ‘daily fasting interval and circadian alignment of feeding act together to extend lifespan 35% in male mice’, Takahashi and colleagues say.

Mice sleep by day and feed during the hours of darkness, the period in which they are most active. How this promotes longevity is hard to explain. The scientists think it has to do with ‘circadian’ rhythms. From the Latin ‘circa diem’, meaning ‘around the day’, these 24-hour body cycles affect sleep patterns appetite and mood. If you function best in the morning, you’re a ‘lark’. Preferring to work in the evening makes you an ‘owl’.

Cat-napping at work is frowned upon, but offenders are in good company; Charlemagne, his biographer Einhard wrote, ‘would remove his shoes and undress completely, just as he did at night, and rest for two or three hours in the afternoon'.  Tell that to the boss the next time he catches you nodding-off at your desk.

So when should we have dinner?

Our body-clocks evolved when we were hunter-gatherers long ago. Unlike other mammals at the top of the food-chain, we were able to remain active through the heat of the day. By walking upright on two legs, we kept our heads well clear of the sun-baked ground, dissipating the heat of our huge energy-guzzling brains in the cooling breeze. Sweat, evaporating from our largely hairless skin, lowered our temperatures. Engaged in a high mobility food-gathering regime, what scope was there for feeding on the hoof?

We had mastered fire. Did we eat raw animal prey on the spot, or drag it, and vegetables, back to camp to cook it as darkness fell?

Bon appetit!

[Victoria Acosta-Rodrigues et al. Circadian alignment of early onset calorific restriction promotes longevity in male mice. Science. 2022]