Is a very low-carb diet suitable for you? What are the pros and cons and what you should expect from it? These and other questions are answered by Franziska Spritzler from Low Carb Dietitian. Franziska is a certified dietitian and has personal experience with very low-carb ketogenic diets!
Very-low-carbohydrate ketogenic diets (VLCKDs) have been around for hundreds of years and were the standard form of treatment for diabetes prior to the discovery of insulin in 1922. William Banting, a British undertaker, deserves credit for developing the first VLCKD for weight loss in the mid 1800s. Cardiologist Dr. Atkins popularized it again in the early 1970s after reviewing decades-old nutrition research in his attempt to discover a plan that would allow people to lose weight without going hungry – his own Achilles' heel when it came to sticking to a diet. Over the years, the very-low-carbohydrate ketogenic diet has been criticized for being too restrictive, difficult to maintain long term, and unhealthy. However, many people find that this way of eating is the only one that allows them to lose weight and effectively control diabetes.
How is a Very-Low-Carbohydrate Ketogenic Diet Defined?
Although at this time there isn't universal agreement on the term, a few years ago leading researchers in the field of carbohydrate restriction proposed the definition of very-low-carbohydrate ketogenic diets as those containing less than 50 grams of total carbohydrate per day. However, the degree to which carbohydrates need to be restricted to induce ketosis varies from person to person. Some may achieve elevated ketone levels consuming 60 grams of carbohydrate or more, while others may need to restrict carbs to less than 30 grams or even less than 20 grams to experience the same effect.1
Net or Total Carbohydrates?
Many people count net carbohydrates by subtracting fiber from total carbohydrates, but there are differences of opinion regarding whether fiber should be counted. Soluble fiber may be absorbed and therefore could affect ketosis and blood glucose levels, while insoluble fiber simply passes through the GI tract unabsorbed. Most foods contain both types of fiber, as shown in this comprehensive chart. In their excellent book The Art and Science of Low Carbohydrate Living, Dr. Steve Phinney and Dr. Jeff Volek recommend 50 or fewer grams of total carbohydrates per day on a LCKD and do not mention fiber or net carbs in this regard. However, it stands to reason that consuming 50 grams of total carbohydrate where half or more of the carbs come from fiber will lead to higher ketone levels than if the same person consumes a 50-gram total
carbohydrate diet containing only a few grams of fiber.
Why Follow a VLCKD?
I'm a registered dietitian who eats a diet containing less than 50 grams of total carbs daily and recommends carbohydrate restriction for people who want to lose weight, control diabetes, improve symptoms of PCOS (polycystic ovary syndrome), or experience better overall health. However, there's a lot of controversy around this way of eating. As with any dietary approach, there are advantages and disadvantages to limiting carbs to very low levels.
Very-Low-Carbohydrate Ketogenic Diets: Pros
You'll have an easier time losing weight
Very-low-carbohydrate ketogenic diets are well-known for their effectiveness at achieving weight loss. The exact mechanism for how this occurs is debated among the experts, but it appears to be a result of several factors, including increased satiety, lower insulin levels, and increased lipolysis, or fat breakdown. In fact, in every study – including the “gold standard” for evidence, randomized controlled trials – VLCKDs perform at least as well and generally better than low-fat diets for this purpose. For instance, the A-Z study followed overweight women randomized to one of four diets: Atkins, Ornish, LEARN, or Zone. At the end of the year-long study, the participants on the Atkins diet had lost the most weight, although their carb intake gradually increased from very low levels initially to moderately low (110-140 grams of total carbohydrate) at the one-year mark.
In addition to formal research, there is an impressive amount of anecdotal evidence supporting carb restriction for weight loss and maintenance. For example, the Active Low-Carber Forums website has over 98,000 members, many of whom have lost 50 pounds or more and kept the weight off for several years by adopting a VLCKD.
Your blood sugar levels will become more stable
Carbohydrate is the nutrient with the largest impact on blood sugar; for those with diabetes, consuming even modest amounts can raise blood sugar to levels that damage blood vessels and nerves. Elevated blood sugar also places a heavy burden on the beta cells of the pancreas to produce high amounts of insulin in an attempt to shuttle the sugar into the body's cells. Following a VLCKD is the most effective strategy to reduce postmeal blood sugar response – as well as the safest, given that insulin and all oral diabetes medications carry some risks. Dr. Eric Westman of Duke University has conducted studies in which people were able to reduce or significantly decrease diabetes treatment by following a diet containing less than 20 grams of total carbohydrate per day(in this study and also here).
Your body composition will probably improve
Although in some circles low-carb diets have a reputation for inducing muscle loss, research has demonstrated the opposite: A very-low-carbohydrate ketogenic diet promotes better retention of muscle mass during weight loss and overall improvement in body composition.
Your risk for heart disease may go down
People who restrict carbohydrates and increase intake of healthy fats like olive oil, coconut oil, butter, lard, tallow, avocado, olives, and nuts almost universally experience a drop in triglycerides and an increase in healthy HDL cholesterol. In addition, VLCKDs promote large, fluffy LDL particles (Pattern A) which are relatively benign with respect to heart disease risk, particularly when compared to the atherogenic small, dense type characteristic of Pattern B.
Sounds great, doesn't it? But in the interest of fairness, let's look at potential disadvantages of following a VLCKD.
Very-Low-Carbohydrate Ketogenic Diets: Cons
Your LDL cholesterol might go up
Will a very-low-carbohydrate diet raise your LDL cholesterol? Maybe. LDL cholesterol response to carbohydrate restriction is variable; it's believed that roughly 50% of people experience a rise while the other half either see a decrease or experience no change. However, even if your LDL does go up, it will in all likelihood result in the more favorable Pattern A mentioned above. There is also a temporary increase in LDL following significant weight loss, so keep this in mind. Finally, the LDL-C in most lab reports may not be accurate. It's calculated using total cholesterol, HDL-C, and triglycerides in what's known as the Friedewald equation, and if triglycerides are less than 100, it will overestimate your true LDL level.
Your food choices will be somewhat limited
This is one of the biggest criticisms of low-carbohydrate diets, and there's some validity to it. On a VLCKD, there are several off-limits foods that may include some of your favorites: pasta, rice, bread, most fruit, and sweets. Although there are acceptable substitutes for many of these items, even the most enthusiastic low-carber will admit that there are some foods that simply can't be successfully replaced by a low-carb version, such as bread or baked potatoes.
You'll likely develop a decreased tolerance for high-carb foods
Although people respond to carbohydrate restriction differently, generally speaking, tolerance for carbohydrates usually goes down after becoming keto-adapted. In other words, your blood sugar will rise higher after consuming a high-carb item than it would if you followed a regular diet comprised of at least 150 grams of carbohydrate daily. This is sometimes referred to as physiological insulin resistance in order to distinguish it from the pathological insulin resistance that occurs in Type 2 diabetes, obesity, and metabolic syndrome. Because of this, you're instructed to eat at least 150 grams of carbohydrate for three days prior to taking an oral glucose tolerance test (OGTT), which allows you to regain carb tolerance. If you took the OGTT (which involves consuming 75 grams of straight glucose) without modifying your very-low-carbohydrate diet, your blood sugar might potentially rise to the level where diabetes could be diagnosed (200 mg/dL) even if you don't have diabetes.
You might get constipated
Not everyone who follows a VLCKD develops constipation, but enough do to mention it here. Fortunately, it's often temporary and can be remedied by drinking enough fluid, getting sufficient magnesium, and consuming additional salt – at least 1-3 extra grams per day.
Is A Very-Low-Carbohydrate Ketogenic Diet Right for You?
In my opinion, the benefits of keeping your carbs very low outweigh the drawbacks, but whether to follow a VLCKD is a matter of personal choice. If you love high-carb foods and find that avoiding them inevitably leads to feelings of deprivation which results in bingeing, then a carb-restricted diet probably isn't your best choice. However, if you're trying to lose weight or have diabetes or metabolic syndrome and enjoy rich, luxurious, high-fat foods like cheese, cream, eggs, avocado, and fatty meats – and are willing to give up the aforementioned high-carb foods in exchange – a very-low-carbohydrate ketogenic diet may be the ideal way of eating for you.2
Although VLCKDs are safe and healthy for most people, it's important to speak with your doctor prior to adopting a low-carb diet or making other dietary changes.