Is the slow-carb diet worth trying? Will it help you lose weight? EatingWell explains.

Brierley Horton, M.S., RD
July 14, 2020
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You've no doubt heard of low-carb diets (remember the '90s, when carbs were the enemy?) 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—that is, those refined carbohydrates found in highly processed foods like white bread, pretzels, crackers or cookies—for "slow" carbohydrates that take a longer time to digest, such as 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, and thus, keep 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 stay away from processed, refined carbs and prioritize less processed whole-food sources of carbohydrate.

Pictured recipe: 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 a 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.

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? 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 cutting 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 Chefbut he isn't 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.

What are the specific rules of the slow-carb diet?

Rule #1: Avoid "white" carbohydrates, or anything that is or can be white.

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

Rule #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 #3: Don't drink calories.

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

Rule #4: Don't eat fruit.

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

Rule #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," Ferriss says. "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 can you eat on the slow-carb diet?

If the slow-carb diet sounds a little 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. In sum: 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, kimchee

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.

That said, there is research that shows a one-day "eat all you want" period (also known as a "refeeding" day) could help to prevent your metabolism from dipping and also bolster levels of leptin—a hormone that could help to mitigate the negative effects of longer-term calorie restriction. And, in particular, making your one cheat day a high-carbohydrate day could potentially be the key to the metabolic protective benefits. One study found a high-carb day of eating not only boosts leptin levels, but also slightly boosts metabolism.

That said, the all-out cheat day the diet allows once a week can also be problematic.

"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, 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 our growth, development and general health.

"This now 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.