You'll never see a cave drawing of a smoothie stand. Our primitive forebears didn't have coffee breaks, snack attacks, three square meals, or night caps. Instead, they ate their food when they could forage or hunt it and then toughed it out until the next feast. There's a growing body of research that suggests that restricting the timing of of your meals is as important to metabolic function as what you actually eat.

The Fast Diet, based on research by Dr. Michael Mosley goes really primitive. To follow the regime, you eat normally for five days and then restrict your calorie intake to 500 calories (600 for men) for two days each week. Proponents of intermittent fasting, such as Mark Mattson, chief of the Laboratory of Neurosciences at the National Institute on Aging and a professor of neuroscience at the Johns Hopkins School of Medicine, reason that, "Natural selection would have favored individuals whose brains and bodies functioned well in a food-deprived state." He adds that when the body is metabolically stressed, it starts burning fat for energy.

Some research shows that this approach is more effective than traditional diet plans for losing weight, improves insulin resistance, lowers body fat, and may be protective against certain types of cancer. But is it for everyone? Certainly such a rigid plan should be avoided by anyone who struggles with disordered eating. Furthermore, our paleolithic ancestors didn't have much of a choice about when they had access to food; confronted with the abundance of our modern lifestyles, intermittent fasting requires the willpower of an Olympic athlete. The average troglodyte set loose in a supermarket would more likely act like a contestant in a hot dog eating contest. Intermittent fasting is a lifestyle, not a diet. If you, like me, love to be spontaneous about cooking and eating, self-imposed starvation on a weekly basis sounds downright grim and antisocial. In fact, even writing about it makes me want to go have a snack.

Timing Counts

A more recent version of consciously restricted feeding might be more suitable for the average homosapien. According to the new book, The Circadian Code, by Satchin Panda, an expert on chronobiology (the study of circadian rhythms) at the Salk Institute, you can lose weight, improve sleep, slow the aging process, and even reverse chronic disease such as diabetes, high blood pressure, high cholesterol, heart attack, certain types of cancer, and Alzheimer's disease by aligning your eating patterns with the body's natural 24-hour circadian cycle.

"We've inhabited this planet for thousands of years, and while many things have changed, there has always been one constant: Every single day the sun rises and at night it falls," Dr. Panda said. "We're designed to have 24-hour rhythms in our physiology and metabolism. These rhythms exist because, just like our brains need to go to sleep each night to repair, reset and rejuvenate, every organ needs to have downtime to repair and reset as well."

According to Panda's research, limiting your food intake to an 8-10 hour window, beginning in the morning and ending by early evening, works best with our metabolism. Most people, however, eat over a much longer period. While your first cup of coffee with a splash of milk at 7 am might not contain many calories, its signal that feeding time has begun. Keep grazing throughout the day and into the evening with a nibble of cheese and glass of wine at 10 pm and you've logged 15 hours. Panda believes that this disrupts hormonal function and deprives your digestive system of necessary downtime. "Eating late into the night for 2-3 days in a week is enough to break our optimum circadian code…." He writes. "This may explain the rapid rise in many chronic diseases and the susceptibility to inflammation in modern societies."

Optimizing Your Metabolism

In a study performed in 2012, Panda and his team tested his theory on two groups of genetically identical mice. One group had 24-hour access to high-sugar and fatty foods. The other mice could have the same foods, but only during an eight-hour period. Each group consumed the same amount of calories. The results were fascinating: the time-restricted mice remained healthy, while the others became obese and susceptible to fatty liver and metabolic disease. Based on the encouraging data from this work, the team then designed an experiment on a group of pre-diabetic men. Over a five week period, the subjects consumed a set amount of calories during a 12-hour window. Then, for an additional five weeks, they ate the same amount of calories during a 6-hour window. In the second phase, the researchers found the men gained a number of significant health benefits. They had lower insulin, reduced levels of oxidative stress, experienced less hunger at night, and their blood pressure dropped by about 10 points.

Dr. Panda's book is about more than eating, it's a primer on how to reset your biological clock for overall health and wellbeing. Science is beginning to show us how modern conveniences such as artificial light and central air conditioning and heat have a downside. They can disrupt the natural cues we require, at a genetic level, to function. In fact, the 2017 Nobel Prize in Medicine was awarded to scientists who discovered the "molecular mechanisms controlling circadian rhythm." Now, if only my inner cave woman didn't get the munchies at 11 PM.