Low-carb diets have been getting more and more popular in the last couple decades. Robert Atkins kicked things off in the ‘90s with his virtually carb-free Atkins diet. The Paleo lifestyle, by and large, involves being mindful of your carbs. Keto, the lowest-carb diet of them all, is helping people shed a few extra pounds. All these diets involve cutting back on carbs, and they can be excellent ways to eat.
Does that mean carbs are bad?
Not at all. In our guide to fats, we emphasized that fat itself isn’t good or bad – it depends on the type of fat and how much of it you eat. It’s the same story with carbs.
Let’s take a look at the different types of carbs, and what each type does in your body. You’ll also learn how to find the right carb intake for you – whether it’s high, low, or in between. Here’s what we’ll cover:
- The three main types of carbohydrate
- Simple carbs
- Complex carbs
- Resistant starch
- How to find your ideal carb intake
Let’s get started.
The three main types of carbs: simple carbs, complex carbs, and fiber
Broadly speaking, you can break carbohydrates down into three classes: simple carbs, complex carbs, and fiber.
Simple carbs (also called refined carbs) are smaller molecules that have already been refined – think sugar, white bread, white rice, and pasta. You digest simple carbs very quickly, with almost no effort.
Complex carbs are larger, more complicated molecules; their complexity means they take longer to digest. Vegetables, potatoes, whole grains, and squashes all contain complex carbs.
Fiber is a class of complex carbs that your body can’t break down. Humans lack the enzymes to digest fiber, which means it passes through your stomach and small intestine more-or-less intact. But while you can’t break down fiber, the bacteria in your GI tract are pretty big fans of it. Feeding your gut bacteria with certain types of fiber can have pretty cool health benefits.
Fiber aside, your body will eventually break down all the carbs you eat into glucose, a type of sugar. Your body then turns glucose into glycogen and stores it for the next time you need a bit of energy. Glucose and glycogen are your body’s main fuel sources (unless you’re on a very-low-carb diet).
So whether you’re eating broccoli or corn syrup, your body will end up with glucose eventually. But there are some major differences in the way simple and complex carbs affect your hormones and digestion. Let’s take a look at simple carbs first.
Simple carbs for quick energy (but watch out for the crash)
Simple carbohydrates break down very easily in your body. They’re already so close to glucose that you hardly have to digest them.
Simple carbs zoom right through your digestive system and build up in your bloodstream. What little digestion they need happens in your small intestine: enzymes break simple carbs down into sugars. The sugars then absorb into your bloodstream through your intestinal wall, and your blood sugar (you may hear it called blood glucose) level rises.
That spike in blood sugar means that, all of a sudden, your cells have tons of glucose at their fingertips. Ever had a sugar high? It happens because your cells start grabbing as much sugar as they want from your blood and turning it into energy.
But if you’ve had a sugar high, you know that a crash usually comes afterward. That’s because high blood sugar also affects your hormones.
- Insulin. High blood sugar is dangerous, so your body sends in the hormone insulin to clean it up. Insulin pulls sugar from your blood and stores it as body fat. In small doses, this isn’t a problem. But in response to a high spike in blood sugar, your body will often release extra insulin, to clear the sugar as quickly as possible. The insulin ends up pulling more sugar from your blood than you want it to.
- Ghrelin. When insulin pulls too much sugar from your blood, the sugar high turns into a crash. Now you have low blood sugar, which makes you feel exhausted and signals that you don’t have enough energy. Your body responds to low blood sugar by releasing ghrelin, another hormone. Ghrelin gets rid of the extra insulin that’s making your blood sugar too low… but ghrelin also makes you hungry (in fact, it’s nicknamed “the hunger hormone”) . You still have extra sugar that you stored as body fat, but you’re tired and hungry, and your brain is telling you start eating again.
The rollercoaster of energy highs and lows is the problem with simple carbs. Simple carbs spike your blood sugar level to an unnatural high, and your body overcompensates by bringing it down to an unnatural low.
That doesn’t mean you should never have a bowl of white rice again. A few refined carbs here and there won’t kill you, but we bet you’ll feel the difference if you try keeping them to a minimum.
Complex carbs for slow-burning energy
Imagine building a fire. Simple sugars are like kindling – they’ll burn bright and fast, but they’ll be gone in a flash. Complex carbs are like a solid log of wood – they’ll burn slowly, providing the fire with fuel for a good long time.
The difference in how carbs burn comes down to structure. While simple carbs are small, easy-to-digest sugar molecules, complex carbs are a bunch of sugar molecules strung together with bonds. It takes a while for your digestion to break through the bonds and pull off the sugars, so you won’t get a big blood sugar spike with complex carbs. They offer more sustained energy and satiety, with more gradual insulin release.
There are three main types of complex carb: fiber, resistant starch, and edible starch. Fiber and resistant starch are complex carbs that you don’t turn into energy. We’ll talk about them in a minute. For now, let’s focus on edible starches, the complex carbs that you do burn for fuel.
Starches are large webs of individual sugar molecules woven together. All digestible starches are made of two major compounds, in differing amounts:
- Amylopectin, the first part of edible starch, has a bunch of branches coming off it, much like a tree. All those branches are entry points for digestive enzymes, so your digestive system attacks amylopectin from all sides and gradually breaks it down.
- Amylose is the second part of edible starch. While amylopectin branches, amylose is a single chain of tightly packed sugar molecules. It doesn’t have a bunch of sites for enzymes to latch onto, so it breaks down very slowly.
- Long-grain brown rice
- Boiled white potatoes
- Sweet potato
- Green bananas
- Whole-grain wheat (make sure you’re not sensitive to gluten!)
Carbs may make up 5% of your diet. They may make up 50%. No matter the total amount of carbs you eat, try to make the majority of them complex. Bonus points if you opt for high-amylose complex carbs. They’ll keep your blood sugar more stable.
Resistant starch for a stronger gut
Resistant starch is a special type of carb that resists digestion almost entirely. Resistant starches avoid breakdown in your stomach and small intestine; they reach your large intestine mostly intact, where they become food for your gut bacteria.
Not surprising, then, that resistant starch can play a big role in gut health. Your gut bacteria ferment it into short-chain fats that repair the lining of your intestines, maintaining gut integrity [4,5]. It may also help remove harmful gut bacteria – cholera, for example, will bind to resistant starch molecules in the gut and become inactive .
Good sources of resistant starch are:
- Green banana (we use green banana starch in Ample)
- Cassava starch
- Raw potato starch (here’s a good source)
You can also increase the resistant starch in rice and potatoes by cooking them and then cooling them. Remember the amylose you were reading about earlier? There’s a lot of it in rice and potatoes, and when you cook amylose and cool it, it packs together even more tightly and becomes a potent resistant starch.
Fiber for fat loss and satiety
Fiber is the last type of carbohydrate we’ll talk about. It’s unique in the carb world. Sugars and starches break down into energy, and resistant starches partially break down. Fiber doesn’t break down at all.
Humans lack the enzymes to digest fiber, so it passes through your small intestine unscathed. Some fibers become food for your gut bacteria, much like resistant starch does. Other fibers don’t – they simply pass through you. That may not sound particularly health-promoting, but it turns out there are a few major benefits to fiber:
- Nutrient absorption. Fiber slows down digestion so you pull more nutrients from your food .
- Satiety. Fiber makes meals more satisfying, even though it doesn’t contain any calories. High-fiber meals inhibit ghrelin, the hormone that makes you hungry, for several hours after you eat .
- Fat loss. High-fiber diets lead to gradual fat loss over time [11,12,13].
- Inflammation. Eating adequate fiber decreased C-reactive protein, the main marker of inflammation, by 63% . That’s huge.
And because fiber doesn’t turn into glucose, it doesn’t count as a carbohydrate in diet. Even if you’re on a very-low-carb diet, you’ll benefit from getting lots of fiber.
Veggies are the best source of fiber. Aim for 6-10 servings of greens a day; that should fulfill your fiber needs. And if this piqued your interest, we have a more in-depth look at fiber here.
How to find your ideal carb intake
We’ve covered the four main classes of carbohydrate: simple carbs, complex carbs, resistant starches, and fiber. The question that follows, of course, is: how many carbs should you eat?
It’s hard to say. There’s no one perfect diet – nutrition varies a lot from person to person. What we can offer, though, are a few different frameworks for you to try. Here are several worthwhile diets, from lowest-carb to highest-carb. Follow the links for guides to each:
- Keto (very low carb, very high fat)
- Slow-carb (emphasis on slow-digesting carbs)
- High-carb, low-fat
Try these diets out and settle on one that makes you feel good and keeps you in shape. And regardless of how many carbs you eat, we suggest sticking to complex sources, preferably from whole foods. Good options are:
- Sweet potato
- White potato
- Green veggies
- Low-sugar fruits like strawberries, raspberries, and blueberries
Any questions about carbs? Comments? Leave them below. Thanks for reading!