Over the last couple of years I have experimented with carbohydrates in a variety of ways. I have done the low carb GAPS intro diet. I have done a medium-low carb GAPS full diet. I have done a medium-low carb Paleo diet. And now I am on a moderate carb Paleo-esque diet. So I've seen many sides of the carb equation, and I've come to a few conclusions by experimenting on myself. While I think that the Paleo or Paleo-esque diet is ideal for most CFers, I am not as convinced that a low-carb version of Paelo is a good idea for us.
I wanted to try a low-carb GAPS/Paleo diet because I was concerned about taking insulin for my CF-related diabetes (CFRD). I was diagnosed with CFRD about 6 months after starting my first GAPS intro diet. I had been glucose-intolerant/pre-diabetic for many years, and so the CFRD diagnosis seemed an inevitable consequence of the progression of my disease. I decided that I was going to try to treat my diabetes with diet alone, by restricting carbohydrates in order to balance my blood sugars. Furthermore, research shows that consistently high blood sugars and the ingestion of simple sugars (especially refined sugars) can harm the immune system and make one more susceptible to infection. I didn't want to stick myself with needles if I didn't have to, and I wanted to reduce my risk of infection and my inflammatory burden. So I thought I'd give the low-carb GAPS/Paleo diet a try.
My Low-Carb Experiments
When I went on the GAPS diet and transitioned to a low-carb (i.e. less than ~100g carbs per day) Paleo diet, I lost a lot of weight within a couple of months. Although all other aspects of GAPS and Paleo diets were fantastic for my body, I restricted carbs too much in the beginning of my dietary transition. I ate too few carbs and tried to replace those calories with fat, but this was not a good long-term solution for me. In the intro diet to GAPS, carb restriction is a part of the procedure to try to correct gut dysbiosis. But after the intro diet, and after the more severe digestive symptoms had resolved due to this dietary change, I should have added in more safe carbs in order to maintain my weight and to provide me with more energy. The hard truth was that I couldn't maintain my weight while also trying to regulate my blood sugar with carb restriction. The easiest way to gain or maintain weight is to eat carbs, as anyone who has studied metabolism knows, and so it is very hard for CFers to maintain weight on a low-carb diet, even if fat intake is high. We just don't digest and absorb fat well enough to have it replace carbohydrates as a calorie source.
Of course, the degree to which this is true depends largely on the person, their age, their activity level, their climate, their level of infection, and many more factors. So the ability for a CFer to thrive on a low-carb, high-fat Paleo diet depends largely on one's individual situation. What didn't work for me may well work for you. But given the generalized physiological truths that we know about CF metabolism and digestion, it is my belief that most CFers would not benefit greatly from a low-carb diet. However, I do believe that many CFers would benefit from a moderate-carb Paleo diet (~100-200g carbs per day), as long as their blood sugars are kept under control.
A Move Towards A Moderate-Carb Diet
Several months into my low-carb experiment, my HA1c was higher than it was previously, and my blood sugar was getting harder to control with diet alone. So I decided to use a little insulin here and there while still keeping a close eye on my carb intake. I noticed that if I used a combination of cinnamon and insulin, this was particularly helpful at keeping my blood sugars stable throughout the day. I also noticed that on a moderate carb diet, I was gaining my weight back without trying very hard. As I have chronicled before, it was very difficult for me to maintain my weight on a high-fat, low-carb diet. I had to try really, really hard to shove in as much fat as possible throughout the day, and still it wasn't helping. When I began to add a bit of rice and potatoes back into my diet, I began to gain weight much more easily. All the while I kept a very close watch on my blood sugar, and began to take more and more insulin to match the increased carbs that I ate. My HA1c remains stable as long as I take enough insulin at the appropriate times. I have not noticed any change in my infection burden related to my increased carb intake. My energy levels have definitely improved, and I very rarely feel the fatigue that used to be my daily companion. I feel like I have more than enough energy to get through my day now. I believe that this is partly due to the great diet that I'm on and the increased carbs, but also largely due to my daily exercise regime and my increased physical fitness.
I am less strict about adhering to the orthodox "Paleo rules", and allow myself to eat pretty much any starchy vegetable, including potatoes, as well as most gluten-free grains, in moderation. My digestion has greatly improved in the last year and these are pretty easy for me to digest now. But I still do not tolerate any dairy at all. I eat legumes (mostly lentils) once every few weeks with no ill-effects, and I do allow myself to eat fermented soy products (gosh, I LOVE tamari!). I still avoid sugar and refined sweeteners, though I do have some honey in tea maybe once a week. In the summer I was eating fruit more frequently (not anymore since it's not in season), and I allow myself to drink some local apple cider once in a while (it's a handy thing to keep around in case I have a random hypoglycemic episode).
For Those CFers Who Are Glucose Intolerant But Not Yet Diabetic
This is a tough situation. On the one hand, controlling carb intake is going to be a really important thing to start getting used to, just in case diabetes does develop. On the other hand, you don't want to restrict carbs and risk losing weight unnecessarily. Regardless, sugar, refined sweeteners, and refined carbohydrates should be minimized or eliminated altogether. This step may be even more important for those who are in the pre-diabetic zone than those who are already taking insulin. I don't think a low-carb diet is necessarily going to be useful for folks in the glucose-intolerant/pre-diabetic group, but a carb-conscious diet is a definite must. Being conscious of what types of carbs and when you eat them is going to be very important. In addition, exercise is a really useful tool here. Remember that exercising muscle can suck up glucose from the blood without the presence of insulin. In other words, exercising if you have high blood sugar (like after a meal) is going to reduce your blood sugar regardless of your pancreas' ability to produce insulin. So exercise after a carb-heavy meal! Even a 10-minute walk will help. Also, I have found that taking cinnamon with carbs is really helpful in keeping blood sugars stable and reducing post-meal glucose spikes. For those fortunate CFers who have very little trouble maintaining their weight, or even need to lose a few pounds, trying a low-carb Paleo diet may be very useful in helping to control their blood sugar or delay the onset of diabetes.
Other Reasons to Go Low-Carb
For the general non-CF population, there are many other reasons to go low-carb, either over a limited time period as a treatment plan for a specific ailment, or as a long term solution to treat or prevent the development of a chronic condition. Low-carb Paleo diets are especially useful for weight-loss and for addressing chronic inflammatory diseases, heart disease, type 2 diabetes, metabolic syndrome, and cognitive impairment diseases such as dementia, Alzheimer's, and even epilepsy. Chris Kresser has researched and written extensively on the subject, so I will refer you to his website for more information.