From what to eat before a date... to the best diet if your family is prone to cancer

...and more insights from the book that promotes a new way to think about food.

Published 28 Feb 2019, 14:55 GMT
Photograph by Mark Thiessen

Dr Michael Roizen is chief wellness officer at the Cleveland Clinic and a New York Times best-selling author. Dr Michael Crupain is chief medical officer for television’s The Dr. Oz Show. Both have long linked a better diet with better health. But their new book, What to Eat When, says emerging science confirms that “when you eat is as essential as what you eat for maintaining a good weight, preventing and curing some diseases, and living a long, energetic, and happy life.”

To coincide with the book’s UK release, the doctor-authors answered questions for National Geographic.

What to Eat When: A Strategic Plan to Improve Your Health & Life Through Food, published by National Geographic Books, is available now here.

Tell us about the science behind your approach to eating.
We’re all familiar with our biological clocks—the circadian rhythm that sends out chemical signals at certain times to help us wake, sleep, and do other activities. Well, we also have a food clock with a similar purpose: to sync our consumption of food with chemical reactions in the body.

According to these clocks, the optimal way to eat is to consume more energy earlier in the day and less energy later in the day. But our bodies crave the opposite—more calories at the end of the day and fewer in the morning. This is a holdover from a time when humans’ food supply was unreliable and storing energy was an advantage. Today this schedule of eating has negative effects on our health: Studies in animals and humans have associated it with weight gain, chronic disease, and premature ageing.

So we need to override that craving-driven schedule and eat in a way—more early, less later—that aligns food patterns with our internal clocks. We call this chrononutrition.

What are the guiding principles in this system of eating?
A few adjustments to existing eating habits will help sync up our internal systems. Two are especially important:

1) Limit your eating to when the sun shines—a window of about 12 hours or, better yet, fewer. That means cutting out nighttime refrigerator raids.

2) Eat more in the morning and midday and less later on. Your body will work best—and be healthier—if you pre-load calories rather than save them until later in the day, as many of us do.

We help people learn how to do this day to day. But we also define “when” another way. Our bodies change depending on what’s going on in our lives—so we may need to adjust what we eat to be at our best. In the book we list common situations, suggest the best things to eat to prepare for them, and explain the science behind our advice.

What benefits do you tell people they’ll derive from eating this way?
The endgame is that this way of eating will extend your own endgame. It will help prevent disease and, in some cases, even curb or reverse disease. Following this plan can result in all kinds of improvements to your quality of life: better sleep, more energy—and just overall better health.

Scroll down for some quick dietary tips...

Photograph by Rebecca Hale, National Geographic

What to eat when... you’re hangry

Roasted chickpeas. They have healthy protein and fibre plus the crunch and satisfaction that hungry, angry people crave. 

What to eat when… you’re going on a first date

Calm nerves with pre-date foods that increase energy levels slowly: avocado, walnuts (good fats), and sliced turkey (healthy protein) on wholegrain toast (complex carbs.)

What to eat when… you’re sick

Granny was right: Chicken soup is helpful, for a couple of reasons. It affects the viscosity of mucus, and it contains ingredients that have anti-inflammatory properties. 

What to eat when… your family is prone to cancer

Lots of vegetables, especially cruciferous ones (cauliflower, cabbage). They’re loaded with disease-fighting nutrients. 

What to eat when… you have a job interview

For breakfast, sprinkle porridge with ground flax seed, a source of healthy fat and vitamins that help boost concentration and cerebral cortex function. Coffee helps sharpen attention and problem solving; have one or two cups – no more – 45 minutes before the meeting. 

What to eat when… you want to look after your brain

Salmon contains the healthy fats that have been shown to protect your brain against memory-related problems. A favourite of Roizen’s: salmon burgers for breakfast. 

What to eat when… you get a lot of headaches

Spinach. It contains B vitamins and other nutrients that have been shown to help reduce the incidence of migraines.


This interview appeared in the January 2019 edition of National Geographic. What to Eat When is available now.


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