Time-Restricted Eating


I’ve talked a lot about time-restricted eating and intermittent fasting in blogs and podcasts, and today I’d like to highlight a brilliant article from Dr. Felice Gersh, M.D. Her information uses science-based principles to separate fads from fiction.

Here’s what Felice said in a recent Medium feature… 

Fasting is definitely trending these days, but the subject is fraught with misunderstandings of the physiological processes involved, having been interpreted and developed by so many using incorrect terminology and flawed information — it’s like a game of telephone!

If one wishes to engage in time-restricted eating, I’m here to say — I agree! But a word of warning: time-restricted eating, even when done properly, does not allow one to simply choose any timeframe within the 24-hour day to eat or not eat.

The trend towards skipping breakfast and eating later in the day does not recognize that our bodies are genetically programmed to want to eat within a couple of hours after waking, and that humans do best when beginning the day with food.

And, here’s the rub — most people writing about fasting have no understanding of what our bodies have been evolved to do, or of the genetic programming of our biological clock, which dictates the proper time of day for various activities to be done in order to optimize health — so I’m here to help you sort fasting fact from fasting fiction.

Intermittent Fasting vs. Restricted Eating vs. Periodic Fasting

Many plans confuse intermittent fasting with restricted eating. They are not the same thing! Intermittent fasting is not eating anything for a full 24 hours on selected days of the week, whereas restricted eating is eating only during certain windows of time during the 24 hour day. To confuse things even further, some plans allow eating up to 500 calories in a day and still call it a fast.

Some restricted eating plans sensibly recommend eating healthy, balanced meals, with no snacking at all allowed, while others permit unlimited amounts and types of food, and even constant eating during a short window of time each day, which is clearly not a good idea.

Periodic fasting is used to denote short periods of days of fasting, typically of no more than seven days. The fasting mimicking diet developed at the Longevity Institute would fit into this definition, and lasts for five days.

The biological processes behind fasting

Many studies have shown that food consumption is complex — it’s not just what you eat or how much you eat — or not eat — but the window of the day in which it’s done. It might come as a surprise to you that eating your biggest meal for breakfast vs. eating your biggest meal as a late dinner has quite different impacts on the body.

When you eat in the morning, your body is happy, and the stress hormone cortisol decreases. If you don’t eat for hours, it a signal to the body that food is scarce and it keeps up the cortisol production, as the body has tasks to perform and without new food (energy) coming in, must feed off itself to maintain its energy needs. This sounds good at first until it’s understood that high cortisol increases the disposition towards insulin resistance and breaks down muscle and bone.

Data has been accumulated that those who regularly skip breakfast and eat late at night have a higher incidence of atherosclerosis — a disease in which plaque builds up inside your arteries — even when the same food is eaten but just distributed differently throughout the day, which causes weight gain.

That’s not to say that people can’t lose weight by skipping breakfast if they seriously reduce caloric intake over time, but it is more difficult compared with eating a substantial breakfast and making dinner small.

So, if you work night shifts, you can develop serious metabolic issues with substantially higher rates of diabetes, metabolic syndrome, heart attacks, depression, and cancer. Clearly eating at night and flipping our innate rhythms is a metabolic disaster, so do try and keep meal times as close to the “normal” times as you can.

What is the best way to fast?

The best way is to eat a large, healthy breakfast, skipping lunch — or making it a small fatty snack such as a few nuts, some avocado, or some olives — and then having an early, moderately sized dinner.

Periodic fasting is a great way to improve all the standard measures of metabolic wellness and is the best way to trigger important processes like cell rejuvenation (autophagy), killing off of bad cells (apoptosis), increasing brain growth factors, and even stimulating stem cells to proliferate.

My recommendation

What I choose for myself and my patients is the fasting mimicking diet from the Longevity Institute at USC, now made into a commercial product called ProLon. I care for it so much, I’ve personally done it 13 times and plan to continue with it indefinitely. In full disclosure, I’ve become a paid advisor for them, but only after serving as a volunteer for over a year, implementing it in my practice and providing feedback.

Keep in mind for yourself that the best approach to health is to do what we are designed to do, eat what we are designed to eat, and eat when we are designed to eat. And that means eating breakfast, not snacking, and ending our eating so get 13-hour fast between dinner to breakfast. Breakfast should be eaten within two hours of waking. If you then add periodic fasting, preferably using ProLon for best efficacy and safety, just a few times a year, your body will have the best chance to be optimally healthy, and you’ll have the best chance to lead the vibrant, active, enjoyable life you deserve.