My Thoughts on Low-Carbohydrate Ketogenic Diets

Now that I've finally finished my article for the American Diabetes Association, I'd like to start by expressing my sincere appreciation for those who write scholarly articles and books. The time and effort it takes to produce accurate, substantive work  is much more than many would expect. So to all the authors of my favorite nutrition books of 2011, thank you so much for the time you put in!  My article was only a few pages long and took more hours than I care to admit. Fortunately, doing the research for it provided me with some good ideas for future blogs posts.

I was asked to write the article on a low-carbohydrate diet pattern for blood sugar and weight management in people with diabetes. The amount and type of carbohydrates to prescribe was at my own discretion, and I gave it very careful consideration after reviewing all of the available evidence. Although I've never personally cut carbs to the point necessary to induce ketosis, I was open to the possibility that there was evidence to warrant its use in diabetes and weight management. There has been a lot of research in this area within the past ten years, both short- and long-term studies, and I ended up citing 27 of them in the article.

Traditional ketogenic diets are extremely low in carbohydrates (usually 10-15 grams per day) and have been used since the 1920s for the treatment of childhood epilepsy with very impressive results.  There is also emerging evidence regarding their use in therapy for certain types of cancer and neurological disorders such as ALS and Parkinson's disease. Ketosis occurs when the body shifts from using glucose to ketone bodies and fatty acids as its primary fuel. The level at which this occurs varies somewhat among different people, but it's generally less than 50 grams per day. The most famous low-carbohydrate ketogenic diet (LCKD) is the Atkins Diet created by cardiologist Dr. Robert Atkins in the early 1970s. It is mainly used for weight loss but occasionally for blood sugar control as well. The plan involves starting off at  an "induction phase" of 20 grams of carbohydrates and adding back carbs until reaching a "maintenance" level which is also individualized. Dr. Richard Bernstein, who has lived with Type 1 diabetes for more than 60 years, recommends strictly limiting carbohydates with the goal of achieving normal blood sugar levels. By keeping carbs within 30-35 grams per day and 6-12 grams meal, smaller insulin dosages are needed, resulting in less error in matching carbohydrate intake to insulin and more predictable blood sugars. For people with Type 2 diabetes not taking insulin, very-low-carbohydrate intake prevents post-meal blood glucose spikes.

Is there any advantage to a VLCKD  vs. a diet that is low in carbs but not low enough to promote ketosis?  From the research I've seen, the answer is no with respect to the ketogenic aspect of the diet. The carbohydrate restriction itself is another matter, however. Do Dr. Bernstein and many other people with Type 1 and Type 2 diabetes experience better blood sugar control with carb intake at ketogenic levels? Definitely a very large portion do, but this is due to the diet's effect on blood sugar regulation. For  these individuals, the benefits of VLCKDs may very well warrant its use. But for weight management, I just don't think that's the case. Millions of people have lost weight on Atkins or other low-carbohydrate plans, but many have never achieved their personal weight goals, and most have regained at least a portion of the weight back.

Although it doesn't work for everyone,  I do believe a low-carbohydate diet can help people lose and maintain weight. Starting off at ketogenic levels may provide a psychological benefit due to early rapid weight loss that usually occurs, but there is certainly no indication to remain in perpetual ketosis for weight management purposes. While many low-carb proponents speak of a "metabolic advantage" that occurs with ketosis, characterized as turning your body into a fat-burning machine, I have found no convincing research to support this. It appears that the mechanism responsible for weight loss is a spontaneous reduction in calories due to reduced hunger and greater satiety on both low-carb diets and VLCKDs. And once a person reaches a certain weight, if the caloric intake is too high to promote further loss at this new weight, then weight loss will stall regardless of whether carb intake remains at ketogenic levels or not.

There may be another reason for slowed weight loss on a VLCKD. Recently, there have been several posts on various paleo/ancestral blogs regarding problems people have encountered on low-carb diets. I hadn't really been following this issue that closely since I was doing a lot of lit review for the article. But it seems the main issues people have encountered are failing to sustain continued weight loss despite keeping carbs low, an inability to stay warm, and fatigue. These are symptoms of potential thyroid dysfunction (among other things). There is a good amount of research indicating that people may develop problems converting the thyroid hormone thyroxine (T4) to the active hormone triiodothyronine (T3) and instead convert a greater than normal portion to the inactive form, reverse T3 (RT3) at lower carbohydrate intakes, with the effect being more pronounced at ketogenic levels. In certain individuals this may result in lower resting metabolic rate. It's important to note that this does not happen to everyone on VLCKDs, however, and thyroid function is very complex and affected by many factors in addition to carbohydrate and caloric intake.

I'm sure I'll probably lose several followers after this post, but I have to be honest and state my true beliefs as a dietitian and fellow low-carber. I've never advocated a ketogenic approach for weight management, and I received some very unpleasant e-mails and comments on another member's Facebook page when I recommended staying above 20 grams of carbs per day. (In that post, I neglected to mention the exceptions of treating epilepsy and possibly cancer and neurological disorders).  As an outpatient dietitian in a large hospital, I counsel many people who are not even remotely interested in following a low carbohydrate diet, and that's fine. People can certainly lose weight and even control blood sugar (albeit with larger doses of medication) on a higher carb, lower fat diet.  I'll be the first to admit that if I didn't have blood glucose issues I'd be eating more carbs.

I truly feel that people should listen to their bodies and eat in a way that works best for them. From a personal standpoint, I tried introducing safe starches to my diet  for several weeks after reading about the brilliant Paul Jaminet's Perfect Health Diet and found that I could only tolerate just under 1/2 cup of potato or rice; any more and my blood sugar was well above 140 at the one-hour mark. To me such a small amount just isn't worth the prep time!  So these days the majority of my carbs are coming from all kinds of fruit as well as yogurt. My total carb intake for the day is about 90-100 grams (65-75 grams digestible or net carbs), and this works well for me.  I'd like you to do what works best for you. If you feel great on a VLCKD and are able to achieve and maintain your goal weight by following this plan, that's wonderful. But please be aware that ketosis isn't necessary to achieve weight loss. As with any diet, it is calories in vs. calories out that determines the ultimate outcome on the scale. 

If you're wondering what my carbohydrate recommendations were for the article, as a general guideline I advised  a starting point of about 85-110 grams of total carbohydrates (60-80 grams net carbs) per day using whole, unprocessed foods. (Interestingly, the Atkins website recommends 75+ net carbs daily, including grains, for lifetime maintenance). I know there will be many very-low-carb enthusiasts who think this is far too high, and I'm also expecting a backlash from other dietitians saying it's way too low, unsafe, unsustainable, lacking in nutrients, and, of course, too high in fat and protein. But I feel good about these recommendations given the research I've reviewed along with my own experience and that of others. You know the lyrics from that old song: You can't please everyone, so you better please yourself.



References:
1. Zhou W, et al. The calorically restricted ketogenic diet, an effective alternative therapy for malignant brain cancer.
Nutr Metab 2007; 4:5
2. Zhong Z, et al. A ketogenic diet as a potential novel therapeutic intervention in amyotrophic lateral sclerosis. 
BMC Neurosci 2006: 7:29
3. Johnson CS, et al.: Ketogenic low-carboydrate diets have no metabolic advantage over non-ketogenic low-carbohydate diets. Am J Clin Nutr 2006; 83:1055-1061
4. Martin CK, et al. Change in food cravings, food preferences, and appetite during a low-carbohydrate and low-fat diet. Obesity 2011; 19:1963-19704. 
5. Bisschop PH, et al. Isocaloric carbohydrate deprivation induces protein catabolism despite a low T3-syndrome in healthy men. Clin Enocrinol 2001; 54:75-80