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Fiber on LCHF Diets: Benefits for Weight Loss and Beyond

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Over the past few months, several women have contacted me  expressing frustration at being unable to lose weight despite strictly following a LCHF diet. When I ask whether they’re including high-fiber plants like brussels sprouts, berries, nuts, and dark chocolate, the response is typically, “I avoid those because they’re so high in carbs. I limit my carbs to less than 20 grams total.” This is the trend I’ve noticed lately in the low-carb community: the belief that limiting vegetables and other high-fiber plants in an attempt to keep carbohydrate intake at an absolute minimum (sometimes as low as 10 grams of total carbohydrates per day) long term is the key to losing weight.

Soluble Fiber’s Role in Improving Blood Glucose Regulation

A few weeks ago, Martina from the KetoDiet App website wrote an excellent blog post about counting net carbs vs. total carbs for those following a carbohydrate-restricted lifestyle. In the article, she correctly states that insoluble fiber passes through your system without being absorbed, so it should be subtracted from the total carbohydrate count. In addition, Martina explains that, unlike insoluble fiber, soluble fiber does not pass through the colon but rather is fermented into short-chain fatty acids (SCFAs) by our gut bacteria. 

The principal SCFAs are acetate, butyrate, and propionate. Of these, propionate is the only one that can be converted into glucose via gluconeogenesis (1). But would this have any significant effect on postmeal blood glucose given that most fiber is insoluble and only 15-40% of any soluble fiber will be converted to propionate (2)? Take brussels sprouts, for instance, one of the few foods that contains more soluble than insoluble fiber. A 1-cup serving has about 4 grams of soluble fiber. Less than 2 grams will be converted into propionate, and the amount of glucose produced from it via hepatic gluconeogenesis would be quite small, so serum blood glucose levels wouldn’t be affected much.

More importantly, as Martina pointed out, De Vadder, et al, recently reported the results of a study on mice suggesting that SCFAs promote intestinal gluconeogenesis (IGN), with propionate acting as substrate and butyrate promoting the expression of genes necessary to induce this process. Compared with control mice fed their normal diet, mice who were fed diets enriched with SCFAs and fructo-oligosaccharides (FOS) experienced lower fasting serum blood glucose levels, improved glucose tolerance, and a significant reduction in the enzyme responsible for hepatic gluconeogenesis (3). Essentially, propionate is converted to glucose, which is used within the intestine, decreasing the amount of glucose produced by the liver, resulting in the above-mentioned benefits. Yes, this was an animal study, but it provides an intriguing explanation for the improvement in blood glucose levels seen in human studies examining the role of dietary fiber (4, 5).

Blood glucose response to fiber-rich food may differ among some people with Type 1 diabetes, whose blood glucose levels can reportedly rise as a result of higher food volume in the stomach or other stimuli, regardless of digestible carbohydrate intake. Dr. Bernstein and others with T1 have suggested such a response (what he calls The Chinese restaurant effect), but I know of no studies confirming this and would appreciate references if anyone has them.

Health Benefits of Fiber and SCFAs

We’ve known about the benefits of fiber on colon health for decades. Although it’s believed these are due in part to insoluble fiber’s ability to reduce intestinal transit time so potentially carcinogenic substances in our food spend as little time as possible in our GI tract, more recent research suggests that fiber’s chemoprotective effects may be due primarily to the effects of one of the SCFAs, butyrate (6,7), which provides energy and nourishment for the cells of the colon.

In addition, higher fiber intakes may reduce levels of C-reactive protein (CRP) and other inflammatory markers, improve our immune response, and protect the gut from harmful microorganisms that can make us ill (8). In essence, fiber’s fermentation to SCFAs helps keep our gut well nourished and working the way it should. 

Increasing High-Fiber Carbohydrate Intake May Be Helpful for Weight Loss

Let’s go back to restricting intake to less than 20 grams of total carbohydrates in order to lose weight. When carbohydrate intake is this low, there’s a limited number of foods that can be eaten: meat, cheese, fish, eggs, butter, cream, coconut oil, olive oil, and small amounts of greens and other very-low-carb vegetables. Yes, carbohydrate intake may be well below 20 grams of total carbs daily, but depending on portions consumed, calorie/energy intake  may be too high to promote weight loss. A serving of bullet-proof coffee contains 440 calories, zero carbs, zero protein, and zero fiber.

Aside from fiber’s beneficial effects on overall health outlined above, consuming at least a moderate amount of fiber can facilitate weight loss, and both insoluble and soluble fiber can be helpful in this regard.

Insoluble fiber passes through the body without being absorbed. It adds volume to meals, but zero calories and zero carbohydrates. In fact, you could almost say that insoluble fiber provides negative calories, in that it may lower the amount of energy derived from fat and protein when all three are consumed at a meal (9).  Most foods are higher in insoluble than soluble fiber, with a few exceptions (Please refer to Martina’s fiber chart in the blog post linked to above).

Soluble fiber does contribute calories/energy to the body, but no carbohydrates. The chief benefits provided by soluble fiber are due to its fermentation to the SCFAs acetate, butyrate, and propionate, which have been shown to promote satiety, reduce intake, and and decrease body fat (3,10-11).

Carbohydrate and Fiber: What’s Optimal?  

Like carbohydrates, fiber is another substance where across-the-board recommendations can’t be made, but I think it’s best to aim for at least 20 grams daily, with 1/3 or more from soluble fiber. If you’re limiting yourself to less than 20 grams of total carbohydrate, the maximum amount of fiber you can possibly get is 18 grams, and that’s only if the carbs come from foods that are more than 90% fiber, such as chia seeds, flaxseed, or avocado. Generally speaking, those who consume diets containing less than 20 grams of total carbohydrate end up with 10 or fewer grams of fiber. Some people reportedly consume less than 5 grams on a consistent basis.

The goal of carbohydrate restriction is to keep blood glucose and insulin levels low, and this can be accomplished without reducing carbs to near-zero levels. I consume around 30-45 grams of fiber daily, and my net carb intake is around 35-50 grams, so my fiber to nonfiber carb ratio is roughly 1:1. This works well for me, but some people do better with 20-30 grams of fiber and slightly lower net carb intake. People with certain GI disorders* may require restriction of certain types and amount of fiber.

How do you get to 30 grams of fiber yet still maintain net carb intake of less than 40 grams? Here’s one of the sample menus with recipes that will be included in my upcoming book, The Low Carb Dietitian’s Guide to Health and Beauty. 

Sample Low-Carb, High-Fiber Menu

Breakfast:
Cinnamon Flaxseed Pudding*
1 cup blackberries 
Coffee or tea with 2 Tbsp half and half

Lunch:
Insalate Caprese*
1/2 oz dark chocolate (at least 85% cocoa)
Water, tea, or other sugar-free beverage

Snack:
3 celery stalks with 1 Tbsp almond butter

Dinner:
Chicken Curry*
Chocolate Avocado Pudding*
Water, tea, or other sugar-free beverage

Daily totals:
Calories: 1575
Protein: 88 grams 
Total Carbohydrates: 68 grams
Fiber: 31 grams
Insoluble Fiber: 20 grams
Soluble Fiber: 11 grams
Net Carbohydrates: 37 grams
Fat: 108 grams 

Recipes:

Cinnamon Flaxseed Pudding
Number of Servings: 1

Ingredients:
½ cup cottage cheese
2 Tbsp ground flaxseed
½ tsp cinnamon
3 Tbsp chopped toasted pecans
Stevia or other sweetener, if desired

Directions:
Combine all ingredients in small bowl.

Insalate Caprese
Number of Servings: 1

Ingredients:
4 oz fresh mozzarella cheese, sliced into ¼-inch rounds
1 large vine-ripened tomatoes, sliced ¼-inch thick
1/2 cup fresh basil leaves
Coarse sea salt, to taste
2 Tbsp cup extra-virgin olive oil

Directions:
On a plate, alternate mozzarella slice, then tomato slice, followed by basil leaf, and repeat sequence, overlapping each item slightly. Sprinkle salt and drizzle olive oil over top. 

Chicken Curry
Number of Servings: 4

Ingredients:
2 Tbsp coconut oil
1 cup chopped onion
2 tsp sea salt
2 tsp chopped garlic
2 tsp ground ginger
2 tsp coriander
1 tsp turmeric
1 tsp chili powder
4 cups broccoli florets
2 cups snow peas
2 cups mushrooms
½ cup coconut milk
1 lb chicken breast, cut into bite-sized pieces

Directions:
Heat oil in a wok or large saucepan over medium-high heat. Add the onion, then cook and stir until browned. Mix in garlic and spices. Add broccoli, pea pods, and mushrooms. Cook and stir for 1-2 minutes.
Add coconut milk and chicken. Reduce heat to medium and cook for 7 to 8 minutes, until chicken is no longer pink. Stir and remove from heat. Serve immediately.

Chocolate Avocado Pudding
Number of servings: 4

Ingredients:
2 medium very ripe avocados
½ cup unsweetened coconut milk
½ cup unsweetened cocoa powder
1 cup erythritol or other granulated sugar substitute equivalent to sweetness of ¾ cup sugar
2 tsp vanilla extract

Directions:
Cut avocado in half, remove pit, and scrape flesh into food processor or blender. Add coconut milk, cocoa powder, sweetener, and vanilla extract. Process until ingredients are well combined and there are no lumps of avocado. Divide into four dishes and refrigerate at least 30 minutes or until ready to serve.

                                                             
Roasted Brussels Sprouts Recipe

And for anyone who was hoping for a brussels sprouts recipe after seeing the photo and reading about their high soluble fiber content, please check out this delicious side dish, Roasted Brussels Sprouts with Pecans, from Kalyn’s Kitchen.
                                                         
A Balanced Low Carb Diet: Eat Plenty of Plants and Animals

If you’re consuming less than 20 grams of carbohydrate daily and achieving your weight loss goals, I’m very happy for you. But I would consider adding at least a few grams of high-fiber carbohydrates — such as vegetables, berries nuts, and dark chocolate — to optimize overall health and increase your likelihood of long-term success. And if your weight loss has stalled, I definitely recommend increasing your intake of these foods and perhaps decreasing fat and increasing protein intake, depending what you’re doing currently. A  sustainable low-carb lifestyle consists of a balance of nutritious animal and plant foods, based on personal tolerance, preferences, and goals. 

                                                                                 * * *
*For those with small-intestinal bacterial overgrowth (SIBO) or other conditions requiring a low-reside diet, such as acute diverticulitis or other inflammatory bowl conditions, the recommendations for fiber intake provided in this article may be contraindicated. Consult your healthcare provider, who can provide guidance or refer you to a dietitian for recommendations.

References

1.Mithieux G, et al. Intestinal glucose metabolism revisited. Diabetes Res Clin Pract. 2014 Sep;105(3):295-301
2. Bergman EN, et al. Energy contributions of volatile fatty acids from the gastrointestinal tract in various species. Physiol Rev. 1990 Apr;70(2):567-90
3. De Vadder F, et al. Microbiota-generated metabolites promote metabolic benefits via gut-brain neural circuits. Cell. 2014 Jan 16;156(1-2):84-96
4. Post, RE, et al. Dietary Fiber for the Treatment of Type 2 Diabetes Mellitus. J Am Board Fam Med Jan-Feb; 25:16-23, 2012 
5. Aller R, et al. Effect of soluble fiber on lipid and glucose intake in healthy subjects: a randomized clinical trial. Diabetes Res Clin Pract. 2004; 65(1): 7-11
6. Cho Y, et al. Colon cancer cell apoptosis is induced by combined exposure to the n-3 fatty acid docosahexaenoic acid and butyrate through promoter methylation. Exp Biol Med (Maywood) 2014;239(3):302-310
7. Fung KY, et al. A review of the potential mechanisms for the lowering of colorectal oncogenesis by butyrate. Br J Nutr. 2012 Sep; 108(5):820-31
8. Levison ME, et al. Effect of Colon Flora and Short-Chain Fatty Acids on Growth In Vitro of Pseudomonas aeruginosa and Enterobacteriaceae. Infect Immun. Jul 1973; 8(1): 30–35
9. Baer DJ et al. Dietary fiber decreases the metabolizable energy content and nutrient digestibility of mixed diets fed to humans. J Nutr. 1997 Apr;127(4):579-86
10.Darzi J, et al. Do SCFA have a role in appetite regulation? Proc Nutr Soc. 2011 Feb;70(1):119-28
11. Lin HV, et al. Butyrate and propionate protect against diet-induced obesity and regulate gut hormones via free fatty acid receptor 3-independent mechanisms. PLoS One. 2012;7(4):e35240


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17 Comments

  1. Eddie Mitchell says:

    Hi Franziska

    As always a great post. I agree with everything you have said. Throwing my 5 cents in and I appreciate some can benefit from an extremely low carb diet, I reckon 50 net carbs a day is the way to go, for diabetics and non diabetics alike, for the following reasons. The term diet is often used, but for many a complete change of lifestyle is required, for life, especially diabetics. Using around 50 net carbs a day gives a very wide range of foods to choose from and chosen wisely will provide all the essential nutrients for good long term health. Short term fixes do not work for most, but for most, a change of dietary lifestyle has to be satiating and not require iron will power.

    I have adhered to a 50 net carbs per day lifestyle for over six years as has my very slim non diabetic wife Jan. This has resulted in non diabetic blood glucose numbers for me, and has had no measurable down sides whatsoever, as a type two diabetic I have around 50 blood tests via hospital per year.

    I look forward to reading your book when published, alas, I doubt your tips on beauty will be of any use to a grizzled old warrior like me. Many will benefit, of that I have no doubt.

    Kind regards Eddie

    1. Franziska Spritzler says:

      Thank you so much for the nice feedback and continued support, Eddie. I wholeheartedly agree with all of your remarks.You’re a wonderful example of how eating up to 50 grams of net carbohydrates from whole foods can beautifully control blood glucose levels in people with diabetes. And Jan is an ideal representation of the vibrant health, slim figure, and lovely skin women can achieve with the same diet, whether they have diabetes or not.

      Thanks as well for your supportive words about my book. I worked very hard to make it as evidence-based and practical yet inspirational as possible. I hope women enjoy reading it and learn from it as well!

      Kind regards,

      Franziska

  2. I’m glad you brought up this subject. I always seem to be the lone defender of net carbs in the debate, with all the others claiming that fiber raises their blood glucose. For myself, I noticed early on that virtually all types of fiber do not raise my blood glucose, and have since eaten fiber with abandon and not “counting” it at all. I then had to assume that many other people metabolize fiber somehow as they claim it clearly affects them. Or maybe I have not lost as much function yet as they have.

    1. Franziska Spritzler says:

      Thanks so much for your comments, Anna. I’m happy to hear that you’ve not had any problem with fiber raising blood glucose. As I mentioned in the article, some people with T1 have reported BG elevations after consuming high-fiber foods. I would like to see RCTs on people with diabetes exploring this issue and the mechanism behind the response.

  3. Common Sense says:

    Thanks for the interesting article! I’ve tried a variety of carb levels. When I first started keto, I did 20 total grams, then a couple of months later did 30 net grams as I learned more about the lifestyle. I generally fall somewhere between 20 and 30 net and don’t sweat it if I go over over once in a while. I find that resistance and interval training works better to get through a stall than mucking with carb levels (I have about 15 lbs left to lose).

    One of the best fiber sources for me are the products from The Great Low Carb Bread Company. They do contain some gluten, so may not be appropriate for everyone, but a bagel has 16g carbs, 14g fiber for net 2g. Their bread is similar for 2 pieces. Their products are the only lc bread products I’ve tried that actually toast and grill like real bread, the texture is similar too, if a bit drier.

    My usual breakfast is a bagel with cream cheese and butter and an lc yogurt with chopped nuts, and sometimes a sugar-free mocha latte, about 8-10g net for everything. In the summer, I add about 1/2 cup of berries with whipped cream. Since I don’t usually feel the need to eat lunch, that leaves a good amount of carbs available for veggies with dinner, plus an lc dessert. I eat dark chocolate and nuts a lot in my desserts, I also make sugar-free gelatin with berries often.

    Another easy way to get fiber is to make pudding and popsicles with avocado. I’ve made chocolate and lime and both flavors completely mask the avocado. They are also VERY filling.

    1. Franziska Spritzler says:

      Thanks for your comments and sharing your personal experiences! Most of my readers and clients avoid grains/gluten, but I’ve recommended TGLCBC bagels for the few who do.

      I included a recipe for chocolate avocado pudding in my post, but I never thought about making popsicles. Thanks for the tip!

  4. Part of the problem has been the exploitation of “net carbs” in manufactured products using polyols, fructo-oligosaccharides and the like. Many adopting “Total Carbohydrate” do so as an insurance against dodgy labelling and formulation practices, rather than to limit intake of “proper” dietary fibre.

    1. Franziska Spritzler says:

      Absolutely, Phil. Of course, in England, fiber is never counted as part of the carbohydrates. And if you stick to whole foods, there’s no need to worry about the sugar alcohols that can be absorbed and raise blood glucose, such as maltitol, etc. Thanks for your comments!

  5. Mike Lohre says:

    Nice post I am not a fan of the dogma of low carb nutrition. It very much reminds me of the same dogma that attacked fat and saturated fat in the previous two decades. Advocating healthy eating by avoiding a particular macro-nutrient is not going to cure a global epidemic of degenerative disease that we both agree has its roots in diets of human affluence. We differ in that this low carb movement scares me even more than the low fat movement did. Why? Indisputably, modern diet has gotten out of step with modern human biology, but how can diets that focus on restricting carbohydrate bring us closer to a diet with a hominid foundation in the consumption of a diverse intake of wild tree fruits, leaves, roots and flowers? Yes, sucrose and high-fructose are carbohydrates, but so are most of the calories (and non-caloric fibers) of fruits and vegetables and the foundation of a hunter-gatherer traditional hominid diet. Any issue I ever take with your posts has little or nothing to do with your diet (I think your diet is great and the mission you have adopted to help others improve their lives through nutrition inspires me), it is just a gut reaction to the potential aftermath of the “low-carb” movement, as we are now dealing with the repercussions of the low-fat movement. The article you posted above is an example of these consequences in that a growing number of people are avoiding fruits and vegetables as they are high carb foods.

    1. Franziska Spritzler says:

      Thanks so much for your thoughtful and insightful comments, Mike. I truly appreciate you taking the time to respond, and I agree with much of what you said.

      Best, Franziska

  6. That avocado pudding is delicious, and so easy to make. Thank you so much!

    1. Franziska Spritzler says:

      I’m so glad you enjoyed it, Gretchen!

  7. You always make so much sense in your posts, and I appreciate your thorough research and thoughtful approach.

    I’m eager to try your recipes, so I wonder, would Greek yogurt substitute for the cottage cheese in your flaxseed pudding?

    And what could I add to the caprese salad? Even with all the fat and protein, it doesn’t seem like that much food. Or maybe that’s because I don’t need to lose weight or even maintain–I need to gain.

    I’ve been eating LC/VLC for about 4 years because I’m pre-diabetic. The only downside I’ve experienced is that it’s impossible to gain weight.

    1. Franziska Spritzler says:

      Hi Jkim,

      Thanks so much for your nice feedback and comments.

      Yes, you could use Greek yogurt instead of cottage cheese. It’ll be a bit more sour, but you might prefer it that way.

      Since you’re trying to gain weight, I’d increase the portion size of the cheese and add more olive oil. You could also have about 1/4 cup of nuts (macadamia, hazelnuts, pecans, and walnuts are lowest in net carbs) with the chocolate.

      I hope that helps! Happy New Year!

      Franziska

  8. I decided to try your breakfast using cottage cheese instead of Greek yogurt, and I really like it. But lately I’ve been reading a lot about the insulin spike from eating dairy. Cottage cheese appears to be more problematic than fermented dairy–yogurt or kefir. Would you comment on the insulin spike, specifically as it relates cottage cheese?

    Thanks

    1. Franziska Spritzler says:

      Hi Jkim,

      I’m glad you like the cottage cheese pudding for breakfast. I wouldn’t be concerned about the insulin released in response to dairy, as it’s needed in order for cells to take up amino acids. Beef, fish, eggs, and dairy all cause a postmeal surge in insulin. It’s my understanding that glucagon, the so-called “fat burning” hormone, is also released in response to the dairy protein casein in order to prevent hypoglycemia.

      At any rate, I eat cottage cheese often, and I feel well, maintain good blood glucose control, and stay slim. In most studies, dairy intake is associated with weight loss or maintenance rather than gain. So despite the fact that insulin levels rise briefly to shuttle amino acids into muscle post meal, I don’t think there are any negative consequences, provided carbs stay low to moderate.

      1. Yes, the glucagon released balances out the insulinogenic effect of dairy. Think about it; babies would be very sick if this were not so! 🙂

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