Curious about low-carb diets? Here’s what you need to know

Behold the low-carbohydrate diet—often touted as the golden child of quick weight loss and insulin control plans. But there is a lot of conflicting info out there. Carbs are bad! No, carbs are good! Which is it?! We’re here to tell you that this macronutrient isn’t evil and can even be helpful on a weight care journey for some. But the kind of carbs you eat does matter. So hang tight—we’re going to explain the science.

Why eat a low-carb diet? 

The idea behind eating a low-carb diet is (obvs) to slash eating carbs and instead focus on protein, healthy fats, and non-starchy vegetables. The aim is to cause your body to burn stored fat for energy (instead of its preferred fuel source, which is—you guessed it—carbs) to lose weight. Currently, there’s no set limit for how many grams of carbs you need to stick to for this to happen, but it can range from around 20 to 60 grams a day. And there are a lot of variations on the low-carb diet, including Atkins (where you can have up to 20 grams of net carbs a day during the first phase) and keto (under 50 grams of carbs a day). The pros are that you’re encouraged to eat more whole foods and limit ultra-processed foods (which can lead to weight gain). But the con is that you may cut out many nutritious foods that contain essential vitamins, minerals, and dietary fiber. And as we’ve said more than a few times, research shows that restrictive diets can backfire. 

Let’s take the ketogenic diet, for example. It pairs an extremely restrictive low-carb diet with a high-fat intake. (This can make it unsustainable as a long-term way to eat.)  When you severely limit carbs, it signals your body to break down fat into ketones—putting it into ketosis—because it doesn’t have enough carbs to use for fuel. Ketosis may lead to short-term weight loss (emphasis on short-term) but can have side effects like headaches, fatigue, upset stomach, trouble sleeping, constipation, and bad breath. In the long run, following a keto plan can cause kidney stones, liver disease, and vitamin A, C, K, and folate deficiencies.  

People with type 2 diabetes may try a low-carb diet because carbohydrates raise blood sugar levels more quickly than proteins and fats. The mental math is this: Cut all carbs and manage insulin levels and weight better. But weight loss isn’t that simple.

What carbs are and how they impact blood sugar

Carbohydrates are one of the three main macronutrients your body needs (fat and protein are the other two). They are made up of sugar, starches, and dietary fiber—an indigestible carb. When we eat carbs, they’re broken down into glucose, which is then released into your bloodstream—signaling your pancreas to pump out insulin, a hormone responsible for shuttling the glucose from your blood to the liver, which stores it until you need it for energy. 

Metabolizing carbohydrates is a normal process. Well, usually. It depends on the type of carbs you eat, how often you eat them, and if you can tolerate them well (more on this in a moment). There are two kinds: simple and complex. At Found, we like to call them fast and slow carbs—because the fast (simple) variety can spike your blood sugar levels pretty quickly, while slow (complex) carbs create a more stable release of glucose into your bloodstream. Think of things like sweet potatoes, whole grains, fruit, and veggies. These slow carbs help keep you fuller for longer because of the fiber they contain. And that’s no small win. 

When you eat fast carbs like white bread, cookies, or regular pasta, on the other hand—which are typically ultra-processed—they’re easily digested and bump up insulin levels. Refined carbs can prompt cravings, overeating, and weight gain. A study published in the American Journal of Clinical Nutrition found that participants who ate refined, high-glycemic foods had dramatic blood sugar spikes and crashes that caused increased hunger and food cravings. Fast carbs trigger the pleasure and reward center of your brain, releasing dopamine, a neurotransmitter also released when using drugs or alcohol.  

Consuming fast carbs on the reg can lead to a vicious cycle of long-term elevated blood sugar levels resulting in insulin resistance. Your pancreas needs to pump out lots of insulin to the point where your body can’t respond appropriately anymore. Insulin resistance damages cells, directs your body to store excess glucose as fat, and ups your risk for type 2 diabetes, obesity, metabolic syndrome, PCOS, and heart disease. 

Do low-carb diets really work?

The evidence for going low-carb is mixed when it comes to weight loss—and points to the fact that what works for one person may not work for another. For example, Dr. Rekha Kumar, Found’s Chief Medical Officer, and medical director of the American Board of Obesity Medicine says, “People who are insulin resistant including people with PCOS, prediabetes, diabetes, or even a history of gestational diabetes or a family history of any of these respond well to low glycemic or lower carbohydrate diets.” Meaning, some people may not tolerate carbs as well as others due to their biology and medical conditions.

She also explains that this doesn’t mean doing keto, paleo, Atkins, or never consuming carbs ever. (That would be a drag!) But eating fewer refined carbs, or overall fewer carbs in general will lower insulin over time so the body will release fat better if the reason for increased fat storage is from high insulin. 

A recent systematic review of 61 randomized controlled trials showed that there was little to no difference in weight loss in the short or long term among those who skipped carbs compared to those eating a balanced-carbohydrate diet (meaning healthy, whole-food carbs). And there’s good science that low-carb diets might not be healthy for some. For example, a study of almost 25,000 participants that looked at the long-term effects of a low-carb diet and mortality found an association between those who ate the least amount of carbohydrates and a  higher risk of early death and chronic diseases such as cardiovascular and cerebrovascular diseases and cancer. (An earlier meta-analysis had also shown that low-carb diets may be unsafe in the long term.) 

Complicated info? For sure. That’s why it’s worth talking with your doctor before trying a new diet. But don’t be afraid to eat complex, whole-food carbs on a weight care journey (if you handle them well) and try to figure out what works best for you when it comes to food. Go ahead and fill your plate with lots of whole foods and fiber-rich options.

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