Low carbohydrate and ketogenic diets are often confused, perhaps in part because a ketogenic diet is, by default, also a low carbohydrate diet. That said, there are several important distinctions that set ketogenic diets apart from more generic low carbohydrate diets. Let's look a little more closely at each of those distinctions, so you can better understand why someone might wish to pursue a ketogenic diet.
So, what's a low-carb diet?
Okay, so here's where the greatest confusion generally comes in. A low-carbohydrate diet focuses on limiting carbohydrate intake. A ketogenic diet does the same. So how are they different?
The difference is like that between a doctor and a surgeon. The surgeon is still a doctor but may be far more specialized. Keto diets, similarly, are specialized low-carb diets. So let's look at the generic—the low-carb diet—first.
First, it's important to note that “low” in this case is pretty subjective. There's no clear consensus on how many carbs one can eat before a diet is no longer low-carbohydrate, for instance.
In general, though, the idea here is to be more selective than the standard western diet. Often this means fruits, vegetables, and beans are still acceptable parts of the diet; while grains, baked goods, and processed sugars are either completely eliminated or drastically reduced.
As a result of shifting from carbohydrate-dense foods in your diet, to more low-density foods, the daily carbohydrate quantity you intake is significantly cut.
The subjectivity of the diet, however, can be problematic. For instance, if you were consuming 300 grams of carbohydrates daily, and cut it to 200 grams per day, this is a lower-carbohydrate diet. If you don't replace the lost calories, you may still lose weight, and technically, you could consider this a low carb diet, as you lowered your carbohydrate intake. Conversely, though, if you replace those lost calories with extra proteins or fats, you may have very different outcomes.
As a result, this subjectivity makes it hard to determine whether or not low-carbohydrate diets are effective, as they're not very well defined, and as such, cannot be very well judged.
Then what's the ketogenic diet?
The two biggest differences between low(ish)-carb diets and ketogenic diets are these:
- Low-carbohydrate diets are imprecise; everything in a proper ketogenic diet is measured.
- Low-carbohydrate diets are predicated by cutting back on a single macronutrient (carbohydrates), whereas ketogenic diets require very precise balances of all three.
In short, a successful ketogenic diet is high-fat, moderate-protein, and low-carbohydrate. When done correctly, it allows your body to shift from burning carbohydrates (or glucose) to burning fat in the form of ketones and fatty acids.
In fact, in order for a diet to truly be ketogenic, it has to pursue nutritional ketosis; if it isn't done properly, however, it can go very badly, and leave you feeling terrible—without any of the benefits ketogenesis can provide.
So, how should ketogenesis work?
When ketogenic diets are balanced correctly and appropriately, that carbohydrate restriction should result in increased ketone production. Ketones, which are a byproduct of fat distillation and produced in the liver, can actually be measured (via blood or urine), so if you are a ketogenic diet, you can test progress.
A few guidelines: Traditional western (high-carbohydrate) diets generally result in blood ketone levels between 0.1-0.2 millimoles (mmol), and even moderate-carbohydrate diet (which some may confuse for low-carbohydrate diets, as discussed above) will generally fall in this same range. A truly effective ketogenic diet, however, will result in much higher blood ketone levels, generally above 0.5millimoles but safely as high as 5.0 millimoles. This higher ketone level is a sign that your body has reached a state of “nutritional ketosis,” and shows that the ketogenic diet is working.
But what does this look like as a diet?
For an effective ketogenic diet, consider the following guidelines a starting point for each of the three most major macronutrients.
Standard western diets are frequently between 40-70 percent carbohydrates, by calories. Most research studies equate low-carbohydrate diets as gaining less than 30 percent of their calories from carbohydrates (generally in a range of 50-100 grams per day).
Ketogenic diets, however, often suggest as few as 5-10 percent of your total caloric intake comes from carbohydrates, which is generally in the 25-30 gram range. Many ketogenic plans offer a little more leeway, but almost all suggest a maximum intake of 50 grams on any given day, as keeping carbohydrate intake below that threshold seems necessary for triggering nutritional ketosis, in which your body begins relying on fat for fuel.
This is where ketogenic diets show the greatest range, depending on the goals of the ketogenic diet. If weight loss is the aim, for instance, the plan may suggest moderate to high protein intake, in order to maintain muscle, strength, and satiation, so you aren't left feeling hungry.
Consider the following basic divisions: High-protein diets may recommend 0.7-1 grams per pound of body weight (2 grams per kilogram) or more; moderate-protein diets generally recommend between 0.6-0.7 grams per pound of body weight (1.3-1.5 grams per kilogram); low-protein diets may recommend less than 0.35 grams per pound (0.9 gram per kilogram) of body weight.
One note of caution: As Dr Jacob Wilson, director of the Applied Science and Performance Institute, notes, high-protein diets can make achieving nutritional ketosis impossible. (As a result, he recommends no more than 1.5 grams per kilogram as an upper limit.)
The science behind this is based on a process called gluconeogenesis, by which the body, in a carbohydrate-limited state, breaks down proteins to create glucose, thereby bypassing the aims of ketogenesis, which requires the body not have access to glucose, so that it instead will create ketones for fuel.
When it comes to low-carbohydrate diets, you still need a moderate amount of fat, because otherwise, the only way to get calories is through an overabundance of protein. In a low-carbohydrate diet, though, you're still mostly burning the carbohydrates you're still consuming, so this is less important.
For many people, this is the hardest change to accept when looking at a ketogenic diet. After all, isn't it fat which contributes to obesity? The truth is, the research on high-fat diets are inconclusive at worst, whereas as plenty of evidence suggests that the real culprit for so many health issues is the combination of high-carbohydrate and high-fat diets, or what we might consider a standard western diet.