Most science-based eating plans focus exclusively on foods, that is, which foods to eat. The specialists promoting intermittent fasting look as much at when as at what.
People with the faintest notion that losing some weight might be a good idea, after all of the year’s holidays, are unlikely to cotton to any diet that has “fasting” in its name. But if you’ve read even this far, you likely want to know if this diet allows chocolate and how much. We’ll tell you at the end.
But fear not, this is less about what to eat than when. What’s cool about it is that it’s sufficiently scientific and targeted at the sectors of humanity that have left the caves for good.
We do not look down our snouts at our paleo friends and comrades, but like most eating make-overs, its scheme is largely tacit about timing. Our paleo forbears likely saw the right time to eat as just after clubbing a wildebeest, which does not suggest a breakfast event.
But breakfast is where it’s at with intermittent fasting, or, rather, where it starts. The old nostrum that breakfast is the most important meal of the day has covered a host of sins. And it conveniently leaves out that millions of slim-figured Japanese people think that a nice bowl of glistening fish eyes is a great way to start the day.
What is intermittent fasting?
It will register as either relief or alarm that intermittent fasting isn’t one specific thing. Yet again, you get to play grown-up in operating your body. But you have to concede from the get-go that its acronym, IF, has it all over the competition.
IF refers to any schedule of eating that intersperses times of fasting with times of eating during a specified period. It’s an eating timetable not an eating plan.
One of its forms, 5-2, a variant of alternate-day fasting, had its 15 minutes of fame as the “Hollywood Diet.” But here we’re not considering any schedule that involves whole-day fasting.
We acknowledge going in that fasts of many kinds offer value, but what we’re talking about here is called time-restricted feeding (TRF), but you don’t need to learn the acronym, because we’re not going to use again it because a) it’s the only thing we’re talking about, and b) it sounds god-awful.
It's backed up by studies, but not so much with babies, children, pregnant women, the elderly, and the underweight, all of whom, for obvious reasons, it might harm. Anyone contemplating IF should consult with a doctor, ideally your doctor, before proceeding. As usual, there are variables galore.
A study cited in Wikipedia says “Intermittent fasting has been found in healthy and obese adults to reduce basal insulin, triglycerides, and blood glucose in fasting periods shorter than 24 hours.” Also: "Reductions in weight, improvements in cardiovascular and metabolic variables, such as fat mass, LDL cholesterol, triglycerides, and C-reactive protein in non-obese individuals have been recorded.”
IF usually lead to weight loss, though it’s generally believed that calorie restriction is the best strategy if that is the only goal. That said, the bulk, so to speak, of people who have turned to IF have done so for weight loss and achieved it. Eating at pre-determined periods seems to lead to the intake of fewer calories.
In more detail
Let’s start with the tough stuff: intake during periods of fasting. No one seriously suggests “nothing.” Suggestions range from water, black tea and coffee, and calorie-free drinks, the last a sticky wicket because of the artificial sweeteners usually involved. An infusion of sticks of real cinnamon in hot water would qualify as well and offers strong taste rather than strong aftertaste.
Some plans allow for “modified fasting, which would allow for limited calorie foods and drinks between eating periods, but we’re not talking about those, either.
What we’re specifically discussing here is commonly called the “16-8 method,” or Martin Berkhan’s “Leangains” protocol. There is a concise statement at leangains.com: The fasted phase “should last through the night and during the morning hours. Ideally the fast should then be broken at noon or shortly thereafter if you arise at 6-7 AM like most people. Afternoons and evenings are usually spent in the fed state.”
James Clear puts it at its simplest in “The Beginner’s Guide to Intermittent Fasting”: “I have been intermittent fasting for over one year. I skip breakfast each day and eat two meals, the first around 1pm and the second around 8pm. Then, I fast for 16 hours until I start eating again the next day at 1pm.”
Here’s more in lay language (verbatim): “Your body is in the fed state when it is digesting and absorbing food. Typically, the fed state starts when you begin eating and lasts for three to five hours as your body digests and absorbs the food you just ate. When you are in the fed state, it's very hard for your body to burn fat because your insulin levels are high.
“After that timespan, your body goes into what is known as the post–absorptive state, which is just a fancy way of saying that your body isn’t processing a meal. The post–absorptive state lasts until 8 to 12 hours after your last meal, which is when you enter the fasted state. It is much easier for you body to burn fat in the fasted state because your insulin levels are low.
“When you're in the fasted state your body can burn fat that has been inaccessible during the fed state.
“Because we don't enter the fasted state until 12 hours after our last meal, it's rare that our bodies are in this fat burning state. This is one of the reasons why many people who start intermittent fasting will lose fat without changing what they eat, how much they eat, or how often they exercise. Fasting puts your body in a fat burning state that you rarely make it to during a normal eating schedule.”
What are the main variables?
A daily 16-hour fasting period means an 8-hour eating period. The eight hours are generally referred to as the “eating window.” Which eight hours is the individual’s call. We don’t all get up and go to bed at the same time. A daily strenuous exercise regime may help determine the most appropriate eating window.
Tips on how to make IF work
Why would I do this again?
Because you’ll probably feel better.
People who make a habit of IF cite the following benefits:
You said something about chocolate earlier
Never say never. One day at a time. In moderation. There are very low-sugar chocolates that are not artificially sweetened. (Chocoholics generally think they’re the definition of a bad joke.) All of those and more.
What’s clear anecdotally is that people who make IF their routine have fewer—if any—cravings for high-carb, “naughty” foods. They feel so much better they want less of more.
https://jamesclear.com/the-beginners-guide-to-intermittent-fasting (considers all types of fasting)