Jackie Rodriguez gained 30 kilograms after her first child was born. “I was very unhappy, but I stayed like that for two years,” she says. Then, when her daughter was two, she dropped all the weight with practically no effort. “I wasn’t using any diet pills, fat burners or shakes … nothing,” she recalls.
The transformation had nothing to do with what Rodriguez ate. Rather, it began when she started a new job that shook up her daily routine. Working in the office of a DJ hire company, she started her shift at 5.30pm. Instead of sharing dinner with her husband at nine when he got home from his job as a superintendent, she ate alone at five, before she dropped her child with a babysitter and went to work.
Within nine months, she’d dropped seven dress sizes. She felt like a movie star who seems to lose baby weight effortlessly. “You don’t think that could happen to you,” she says.
Night work often leads to weight gain, so Rodriguez’s story might seem to be a quirk of her particular physique. But unlike many such workers, who labour in the early hours or work rotating shifts, Rodriguez clocked out by 11pm and got a regular night’s sleep. Perhaps even more important, she didn’t eat at work or when she got home – just showered and went to bed.
Rodriguez’s main adjustment was moving dinnertime almost four hours earlier. That single, simple change seems to have triggered her dramatic weight loss – and emerging scientific evidence may explain why.
Is Night Eating Bad?
In laboratories around the world, researchers are developing a completely new understanding of how our metabolism works. It seems that our bodies are primed to process food most efficiently when it’s eaten during daylight hours. “We now recognise that our biology responds differently to calories consumed at different times of day,” says Harvard neuroscientist Frank Scheer.
That means a habit as innocuous as eating at night, compared with eating kilojoule-equivalent meals during the day, may cause some people to gain weight. “That late-night bowl of ice-cream may all go towards your waistline,” says University of California, Los Angeles, neuroscientist Christopher Colwell, the author of Circadian Medicine.
Just look at Satchidananda Panda’s mice. A molecular biologist at the Salk Institute for Biological Studies in La Jolla, California, Panda is a leading expert on how the timing of food intake affects health. His research team has found that mice that are only allowed to eat during a 9-12 hour period (called a ‘time-restricted diet’) during their active phase are drastically healthier and thinner than mice that are allowed to eat the same amount of food over a 24-hour period.
Encouragingly, when unhealthy, snack-around-the-clock mice are put on a strict schedule that allows them to eat only during their active phase, their rates of diabetes and fatty liver disease improve and their cholesterol levels and inflammation markers diminish. “It’s likely we can reduce the severity [of disease] just by changing when people eat,” Panda points out.
The Food-Driven Clock
To understand the connection between meal timing and health, you have to go way, way back in history. The dramatic daily shifts between light and darkness on our planet because of sunrise and sunset have been incorporated into the biology of nearly every living thing.
Our internal organs function differently during the day from how they do at night, in patterns known as circadian rhythms. Over the past few years, researchers have discovered that unnatural light exposure – such as staying up late amid the glare of a TV or a digital screen – disrupts these rhythms in ways that over time can lead to a host of illnesses.
A meta-analysis published in Sleep studying 634,511 people worldwide found that those who frequently miss out on sleep suffer from weight gain and obesity. After a bad night’s sleep, the levels of appetite-triggering hormones in the body increase, while hormones that blunt hunger drop. Peoples’ bodies become resistant to insulin’s effects, raising the risk of fat accumulation, obesity and diseases such as type 2 diabetes.
But now experts have begun to suspect a second circadian clock in the body – organised around food, not light. Scientists still have much to learn about this food-based body clock, but evidence suggests that round-the-clock snacking may pose as much of a danger to our health as artificial light at night. Night eating has been implicated as a factor in diabetes, heart disease, cancer and learning and memory problems.
Throughout evolution, daytime has been for nourishment and nighttime for fasting, and our organs have evolved accordingly. Digestive enzymes and hormones ebb and flow in a predictable pattern over the course of 24 hours, enabling the liver, intestines and other digestive organs to function together as one well-oiled machine. Our modern world of late-night takeaway and snack-filled pantries threatens to upend this calibrating role of food.
“When you eat all the time, your insulin and glucose levels are elevated all the time,” says Ruth Patterson, a nutrition expert and epidemiologist at the University of California, San Diego.
Insulin promotes growth – its constant presence in the bloodstream may give precancerous cells a deadly boost. In new research on breast cancer survivors, Patterson and her colleagues found that breast cancer recurrences were less likely when women abstained from food for at least 13 hours at night.
Gut Rest: How it Works
Compared with other kinds of diets, night fasting is simple. In a small pilot study, Patterson’s team told women to eat dinner as early as 6pm and definitely by 8pm and not to eat again until eight in the morning, for at least 12 hours of ‘gut rest’. “[Fasting] they instantly understood,” Patterson says. “They didn’t have to change what they ate or how they cooked. They would say, ‘If I give my husband a salad for dinner, that doesn’t always fly.’ But when they just said, ‘I don’t ever eat after eight o’clock,’ the men were like, ‘Whoa, tough girl!’ They got respect.”
The new research suggests that breakfast really is the most important meal of the day – but we need to embrace its original meaning: breaking a fast. The first meal of the day is most beneficial only if it comes after 12 to 14 hours of not eating or drinking, says Panda.
In addition to fasting at night, it’s beneficial to eat your main meal earlier in the day. In a 2013 study, Harvard’s Frank Scheer and Marta Garaulet of the University of Murcia in Spain analysed 420 dieters at weight-loss clinics. Participants ate the same number of kilojoules and were equally active, but those who had their main meal before 3pm lost significantly more weight than those who ate later. “To find such big differences in weight loss with just a slight difference in meal timing is quite remarkable,” says Scheer.
To many, the science of meal timing is nothing but common sense. Craig Weingard, a financial compliance manager, is an acolyte to a bodybuilding expert who for years has recommended nightly fasts. For a long time, Weingard resisted. It seemed too painful to go to bed hungry. Finally, he tried it. “In a flash, my whole body changed. I literally can see it the next day when I look at my stomach if I didn’t eat after six,” he says. “Anything that you eat after 6.15pm becomes part of you.”
Use the Food Clock to Lose Weight
- Fast for at least half of each day. Try not to eat for at least a 12-hour span daily. Ideally your fast would begin after the evening meal (from 6–8pm) and extend until breakfast (8am).
- Eat breakfast like
a king and dinner like a pauper. A 2013 Israeli study put overweight and obese women
into two groups. Both had the same number of kilojoules, but one
ate a large breakfast, a medium lunch, and a small dinner; the other had a small breakfast, a medium lunch, and a large dinner. The large-breakfast group lost more weight and showed a stronger improvement in metabolic health metrics.
- Forgo late-night noshing. A 2015 study found that an evening meal raises people’s blood-glucose levels 17 per cent more than does an identical meal eaten in the morning. Related research found that the number of kilojoules people burn digesting food in the first two hours after a meal drops by half if they eat the meal in the evening versus the morning.
- Consume only water during your fast. Anything else will start your body clock. Put off that morning coffee until after your 12-hour window.
- Adjust to your natural rhythms. Early birds might want to eat dinner at 6pm and fast until 6am or later. For night owls, it might be easier to have dinner at 9pm and fast until at least 9am.