The Dangerous Side of Following a Low-Carb Diet

Experts weigh in on the many downsides to this popular and widely misunderstood diet

Can a low-carb diet help you lose weight?

As Brian St. Pierre, a registered dietitian, certified sports nutritionist and coach with Precision Nutrition says, “Of course it can.” But… Well, there are a lot of “buts” that come along with this question because it’s quite a complex topic.

For this reason carbs and low-carb diets are still wildly misunderstood. Most commonly, many people (falsely) believe that eating carbs leads to weight gain. This is a wide misconception and a concept that is simply not true.

“Sure, we can cut carbs temporarily if we need to lose weight quickly,” St. Pierre said. “But for most of us, keeping carbs too low for too long can have disastrous consequences. “This is especially true for those of us who work out.”

If you exercise regularly, and especially at intense levels (think CrossFit) or at a high volume (think marathon training), your body needs more carbs. If you’re less active, St. Pierre explained, your carb needs will be lower. So, just like with most things related to nutrition and fitness, adequate carbohydrate intake is extremely individual.

“Each athlete — each person — is unique when it comes to carbohydrate requirements,” St. Pierre said.

Plus, not only are there a handful of potential negative side effects associated with a low-carb diet, but there’s not much scientific evidence to support its effectiveness as a smart, long-term strategy for eating healthy.

“Does long-term evidence support low-carb dieting?” St. Pierre asked. “Research says no. Over the long haul, any differences between low-carb and other diets even out.”

So, how can you determine the amount of carbs you should be eating, and what are the down-sides and potential health risks associated with decreasing your intake to extremely low levels for extended periods of time?

Here's what you need to know.

The Basics of Carbohydrates

According to the Dietary Guidelines for Americans, 45 to 65 percent of your total daily calories should come from carbohydrates. This range allows for wiggle room since, as we mentioned earlier, adequate carbohydrate intake is unique among individuals and dependent on several different factors, including your activity levels. Some consider consuming below the recommended amount (less than 45 percent) to be a “low-carb” diet, but other protocols have called for less. Essentially, there’s no definitive answer for the amount of carb intake that correlates with a low-carb diet.

“I often hear people make recommendations for the number of grams of carbohydrate someone should eat,” explains Chris Kresser M.S., L.Ac, a globally recognized health and nutrition expert.  “But this is meaningless when you don’t take weight and activity level into account. 75 grams a day may be a moderate-carb diet for a sedentary woman eating 1,600 calories a day, but it would be a very low-carb diet for a highly active male eating 3,000 calories a day.”

This can’t be stressed enough: what’s considered low-carb for one person could be a perfectly acceptable, moderate amount for another. But, at what point can potentially dangerous side effects or, as St. Pierre put it, “disastrous consequences” come into play?

Well, again, it depends on several different factors including your body composition and activity levels, but according to Mark Sisson, author of The Primal Blueprint and creator of, a process called ketosis is triggered when carb intake falls in the realm of 50 to 80 grams per day.

Ketosis is Not Harmful, But There Are Risks Involved

According to WebMD, ketosis is a “normal metabolic process.” When the body doesn’t have enough carbs from food to burn as energy, it burns fat instead, and as a result, makes ketones. If you cut back on your carb intake enough, your body will switch to ketosis for energy. WebMD says ketosis is typically induced after three or four days of eating less than 50 grams of carbohydrates per day and notes that it can become dangerous when there’s a build-up of too many ketones, which could lead to dehydration and even “change the chemical balance of your blood.” Again, ketosis is a normal, mostly safe process, however there are risks involved (especially when the body is depleted of carbs over an extended period of time), which is why it’s recommended that you work with a doctor if you want to follow a “ketogenic diet.” 

Click here to see more of the downsides of following a low-carb diet.

More reading:
Why Calories Matter Less Than You Probably Think
These Carbs Can Actually Help You Lose Weight
Strength, Happiness and 9 Other Exercise Benefits that are Better than Weight Loss