What Is the Slow-Carb Diet?

You’ve likely heard of low-carb diets and the ketogenic diet—which is a very low-carb diet with a few modern variations—but have you heard of the “slow-carb” diet? Unlike a low-carb diet, which is exactly what it sounds like—a diet low in carbohydrates—the slow-carb diet takes a little more explanation. Here’s a look at what it is, how to follow it and why you might consider it.

What Are Slow Carbs?

The slow-carb diet is rooted in the concept of swapping so-called “fast” carbohydrates—those refined carbohydrates found in highly processed foods like bread, pretzels, crackers or cookies made with refined white flour—for “slow” carbohydrates that take a longer time to digest. Slow carbs are those found in vegetables, fruits, whole grains, legumes, beans and grains. Minimally processed foods that haven’t been stripped of nutrients, vitamins and fiber take longer to digest, thus, keeping you feeling fuller longer. They’re also healthier for you.

But the idea of “slow carbs” is more diet fad lingo than it is actual nutrition terminology—so you probably won’t find a chapter on slow carbs in a nutrition textbook. As such—and perhaps not surprisingly—a diet built around the loose concept of slow carbs has even more nuances and restrictions than simply trying to limit processed, refined carbs and prioritize less processed whole-food sources of carbohydrates.

Pictured recipe: Shorbet Ads (Egyptian Lentil Soup)

What Is the Slow-Carb Diet?

While the idea of eating fewer refined carbohydrates and prioritizing whole grains over processed isn’t new, the slow-carb diet embraces a few guidelines that deviate from the general concept of prioritizing whole foods that take longer to digest.

Based on a book called The 4-Hour Body, written in 2010 by Tim Ferriss, the slow-food diet revolves around a principle its founder calls “The Minimum Effective Dose”—that is, doing the smallest amount of work necessary to produce the desired outcome. In this particular instance, Ferriss defines the Minimum Effective Dose (MED) as a pattern of eating that includes following five strict guidelines for six days per week, then taking one day per week “off.”

“The diet emphasizes vegetables and includes plant protein from pulses, like beans and lentils, and allows liberal use of antioxidant-rich herbs and spices. But it’s also too limited and cuts out nutrient- and fiber-rich whole grains, fruit and starchy veggies, like potatoes,” says Cynthia Sass, M.P.H., RD, CSSD, a plant-based performance nutrition coach.

Pictured Recipe: Grilled Chicken with Red Pepper-Pecan Romesco Sauce

On that one day off—your so-called “cheat day”—you’re allowed to eat as much as you want of any food. Ferriss describes it as the day that he “strategically eats like a pig,” which he claims helps him maintain near single-digit body fat percentages. His thinking is that knowing you can eat all you want one day of the week may lower the stress linked with following such a restrictive diet. He also thinks that a “cheat day” may help prevent your metabolism from slowing—a common side effect when you’re eating fewer calories.

The slow-carb diet is generally a low-carb and high-protein method of eating. Ferriss believes that following this pattern of being “on” for six days straight results in weight loss because it prompts the body to use fat for energy, thus breaking down fat stores. And since eating protein is associated with feeling fuller longer, he claims that the diet is a highly effective one for weight loss. (Of note: Ferriss has a podcast and has authored a few other books, such as The 4-Hour Workweek and The 4-Hour Chef—but he is not a diet, nutrition or medical expert.) In addition to the six-days-on, one-day-off schedule, there are a handful of other rules that Ferriss adheres to on the slow-carb diet.

Rules of the Slow-Carb Diet

Rule No. 1: Avoid “White” Carbohydrates or Anything That Is or Can Be White

Most processed carbohydrates are made from refined flour and are pale in color compared to unrefined flours, such as rye or whole wheat.

Rule No. 2: Eat the Same Meals Over and Over Again

Ferriss suggests relying on the same handful of foods that you know adhere to the slow-carb diet requirements, then mixing and matching those foods to build a meal rotation.

Rule No. 3: Don’t Drink Calories

Most drinks provide calories, but little nutrition. Ferriss suggests sticking to water, unsweetened tea, coffee and other calorie-free drinks.

Rule No. 4: Don’t Eat Fruit

Ferriss believes that the natural sugars in fruit may delay weight loss and recommends against eating it.

Rule No. 5: Take One Day Off Each Week

Kick back on one day per week and eat anything you might be craving.

“I recommend Saturdays as your Dieters Gone Wild (DGW) day,” says Ferriss in his book. “I am allowed to eat whatever I want on Saturdays, and I go out of my way to eat ice cream, Snickers, Take 5 and all of my other vices in excess. If I drank beer, I’d have a few pints of Paulaner Hefe-Weizen. I make myself a little sick each Saturday and don’t want to look at any junk for the rest of the week.”

What You Can Eat on the Slow-Carb Diet

If the slow-carb diet sounds restrictive, that’s because it is. Ferriss says he largely mixes and matches from the list of foods below. He chooses one item from each of the three groups, with the starred foods representing foods that he feels are particularly helpful for losing weight.

According to the rules of the diet, you can choose any of the food items and eat as much as you want—but keep your diet simple. Build three or four meals from this list and repeat, repeat, repeat.

Ferriss also recommends eating your first meal within an hour of waking, then spacing your remaining meals approximately four hours apart. He advises eating four total meals a day—so four meals, four hours between each meal.

Proteins:

*Egg whites with 1–2 whole eggs for flavor (or, if organic, 2–5 whole eggs, including yolks)

*Chicken breast or thigh

*Black beans

*Beef (preferably grass-fed)

Pork

*Fish

Legumes:

*Lentils

Pinto beans

Red beans

Soybeans

Vegetables:

*Spinach

*Mixed vegetables

*Sauerkraut, kimchi

Asparagus

Peas

Broccoli

Green beans

Fats in the form of nuts, oils and clarified butter or ghee are also permitted, as well as most spices and some condiments.

Is There Science That Supports the Slow-Carb Diet?

The short answer is no, not really. We couldn’t find any studies that focused specifically on a low-carb/high-protein diet followed for just six days per week.

It’s important to note that diets that restrict calories for six days and then have an eat-anything-and-everything-you-want-until-you-feel-sick day (“cheat day”) are different from diets that restrict calories just for several days a week and eat normally for the other days, known as intermittent energy-restricted diets.

For example, a 2020 study in The Journal of Functional Morphology and Kinesiology suggests that following an intermittent energy-restricted diet for five days a week with a two-day “refeeding” period can help preserve muscle mass and prevent the metabolism from slowing. During refeeding, calories and certain foods can be increased. In this study, carbohydrates were increased during refeeding. But it wasn’t a dieters-gone-wild kind of refeeding.

The all-out “cheat day” the slow-carb diet allows once a week can also be problematic.

A 2022 study in the Journal of Eating Disorders suggests that “cheat days” are linked to eating disorder behaviors and mental health disorders. In other words, regularly incorporating “cheat” days can instigate disordered eating, which, in turn, may increase your chances of it developing into an eating disorder.

“This pattern can lead to overindulging one day a week in ways that leave you feeling bloated and lethargic for a few days,” says Sass. “It can also reinforce a disordered on-and-off eating pattern that can negatively impact mental health and interfere with a healthy social life. It also prevents you from learning how to healthfully incorporate special treats into any balanced day.”

The Bottom Line

Anecdotally, following the slow-carb diet works—if all you’re looking for is a way to lose weight—and Ferriss has ample first-person stories to convince you. However, much like other highly restrictive diets or eating patterns, this one eliminates key foods (hello, fruits and whole grains) that deliver much-needed macro- and micronutrients for your growth, development and general health.

You also need to consider: Is this a way of eating that you could stick with for the long haul? “This now [more than a] decade-old diet is outdated, and any diet that is difficult to stick with long-term is unlikely to support sustainable, healthful weight loss,” concludes Sass.

So while we do advocate for many of the eating patterns that emerge when swapping fast carbs for slow carbs—like eating more whole grains, beans, fruits, vegetables and whole grains—following a restrictive diet that eliminates entire food groups a majority of the time is a tough one for us to get behind as a strategy for long-term success.