Finding yourself confused by the seemingly endless promotion of weight-loss strategies and diet plans? In this series, we take a look at some popular diets—and review the research behind them.
What Is It?
A gluten-free diet is not new. It is the sole treatment for 1-2% of Americans who have celiac disease, a serious condition where the body attacks a protein called gluten, naturally found in many whole grains, causing a spectrum of symptoms that range from bloating to intestinal damage. Up to 6% of people have a related stomach-upsetting but less threatening condition called non-celiac gluten sensitivity. With such a small number truly needing this diet, why have sales of gluten-free products topped $12 billion according to market research?
What is new—and driving these sales upward—is the use of a gluten-free diet for weight loss, partly fueled by celebrity endorsements and personal testimonies of not only pounds quickly shed, but increased energy, improved digestion, and even clearer skin. Consumer surveys reveal that people perceive gluten-free products to be healthier than their gluten-containing counterparts, and almost a third of Americans are now avoiding or reducing their intake of gluten. 
How It Works
A gluten-free diet eliminates all foods containing or contaminated with gluten. Gluten is largely ubiquitous in foods, found as a main ingredient (in wheat, rye, barley, triticale, cross-contaminated oats), in sauces (soy sauce, malt vinegar, flour), and as additives or fillers (maltodextrin, wheat starch). See What Is a Gluten-Free Diet?
When first going gluten-free, perhaps the most noticeable change is having to relinquish favorite staples of bread, pasta, cereals, and processed snack foods. Because some of these products, which are typically highly processed, may be low in nutrients and high in calories, one may feel better and even lose some weight soon after removing them from the diet. Although there are now plenty of gluten-free counterparts to take their place, a gluten-free diet usually causes one to revisit naturally gluten-free whole foods like fruits, vegetables, and grains like brown rice, quinoa, and millet. Including these minimally processed, high-fiber foods may also help to promote weight loss and a feeling of well-being.
The Research So Far
Though research has explored the effects of a gluten-free diet on gastrointestinal disorders, autism, and fibromyalgia, there is none that examines the diet’s effects on weight loss alone or for general health benefits. Because of the lack of experimental studies on weight loss, some researchers have instead examined the long-term effects of people with celiac disease on gluten-free diets, or who are generally healthy and consume a diet low in wheat and other gluten-containing grains. They have found that gluten-free diets: 1) may promote certain nutrient deficiencies, 2) may increase the risk of some chronic diseases, and 3) may actually cause weight gain.
- Intakes of people with celiac disease on a strict gluten-free diet were found to have inadequate intakes of fiber, iron, and calcium.  Other research has found gluten-free cereal products to be low not only in those nutrients but also B vitamins including thiamin, riboflavin, niacin, and folate.
- A study of over 100,000 participants without celiac disease found that those who restricted gluten intake were likely to limit their intake of whole grains and experienced an increased risk of heart disease compared with those who had higher gluten intake.  Many studies have found that people with higher intakes of whole grains including whole wheat (2-3 servings daily) compared with groups eating low amounts (less than 2 servings daily) had significantly lower risk of heart disease and stroke, type 2 diabetes, and deaths from all causes. [4-7]
- Gluten may act as a prebiotic, feeding the “good” bacteria in our bodies. [8-10] It contains a prebiotic carbohydrate called arabinoxylan oligosaccharide that has been shown to stimulate the activity of bifidobacteria in the colon, bacteria normally found in a healthy human gut. A change in the amount or activity of these bacteria has been associated with gastrointestinal diseases including inflammatory bowel disease, colorectal cancer, and irritable bowel syndrome.
- Research is conflicting, but some studies have shown weight gain or increased BMI in people with celiac disease after starting a gluten-free diet. [10-13] This may be partly due to improved absorption of nutrients, a reduction in stomach discomfort, and increased appetite after starting the diet. However, another suspected reason is an increased intake of gluten-free processed food options containing high amounts of calories, fat and sugar.
Gluten-free foods wear a health halo, a belief that a food product is healthful even when it may not offer special health benefits for most people. Research has shown that if one aspect of a food is advertised as healthy or people believe it to be healthy (in this case, the term “gluten-free”), there is a tendency to eat more of it.  This may promote weight gain. Also, an overreliance on processed gluten-free products may lead to a decreased intake of certain nutrients like fiber and B vitamins that are protective against chronic diseases.
Although a gluten-free diet is the primary treatment for celiac disease and may help to alleviate symptoms in various conditions related to gluten sensitivity, there is currently no evidence showing that a gluten-free diet is effective for weight loss or for general health benefits. For individuals who don’t have celiac disease or gluten sensitivity, there is no need to restrict gluten consumption. A healthy dietary pattern typically includes higher amounts of whole grains and lower amounts of refined grains and added sugar.
- Gluten: A Benefit of Harm to the Body?
- Healthy Weight
- The Best Diet: Quality Counts
- Healthy Dietary Styles
- Other Diet Reviews
- Reilly NR. The gluten-free diet: recognizing fact, fiction, and fad. J Pediatr. 2016 Aug 1;175:206-10.
- Niewinski MM. Advances in Celiac Disease and Gluten-Free Diet. J Am Diet Assoc. 2008;108:661-672.
- Lebwohl B, Cao Y, Zong G, Hu FB, Green PHR, Neugut AI, Rimm EB, Sampson L, Dougherty L, Giovannucci E, Willett WC, Sun Q, Chan AT. Long term gluten consumption in adults without celiac disease and risk of coronary heart disease: prospective cohort study. BMJ. 2017 May 2;357:j1892.
- Liu S, Stampfer MJ, Hu FB, Giovannucci E, Rimm E, Manson JE, Hennekens CH, Willett WC. Whole-grain consumption and risk of coronary heart disease: results from the Nurses’ Health Study. Am J Clin Nutr. 1999 Sep 1;70(3):412-9.
- Johnsen NF, Frederiksen K, Christensen J, Skeie G, Lund E, Landberg R, Johansson I, Nilsson LM, Halkjær J, Olsen A, Overvad K. Whole-grain products and whole-grain types are associated with lower all-cause and cause-specific mortality in the Scandinavian HELGA cohort. British Journal of Nutrition. 2015 Aug;114(4):608-23.
- Mellen PB, Walsh TF, Herrington DM. Whole grain intake and cardiovascular disease: a meta-analysis. Nutr Metab Cardiovasc Dis.2008 May 31;18(4):283-90.
- de Munter JS, Hu FB, Spiegelman D, Franz M, van Dam RM. Whole grain, bran, and germ intake and risk of type 2 diabetes: a prospective cohort study and systematic review. PLoS medicine. 2007 Aug 28;4(8):e261.
- Neyrinck AM, Van Hée VF, Piront N, De Backer F, Toussaint O, Cani PD, Delzenne NM. Wheat-derived arabinoxylan oligosaccharides with prebiotic effect increase satietogenic gut peptides and reduce metabolic endotoxemia in diet-induced obese mice. Nutrition & diabetes. 2012 Jan 1;2(1):e28.
- Tojo R, Suárez A, Clemente MG, de los Reyes-Gavilán CG, Margolles A, Gueimonde M, Ruas-Madiedo P. Intestinal microbiota in health and disease: role of bifidobacteria in gut homeostasis. World J Gastroenterol. 2014 Nov 7;20(41):15163-76.
- Gaesser GA, Angadi SS. Gluten-free diet: Imprudent dietary advice for the general population?. J Acad Nutr Diet. 2012 Sep;112(9):1330-3.
- Tortora R, Capone P, De Stefano G, Imperatore N, Gerbino N, Donetto S, Monaco V, Caporaso N, Rispo A. Metabolic syndrome in patients with coeliac disease on a gluten‐free diet. Aliment Pharmacol Ther. 2015 Feb;41(4):352-9.
- Dickey W, Kearney N. Overweight in celiac disease: prevalence, clinical characteristics, and effect of a gluten-free diet. Am J Gastroenterol. 2006 Oct;101(10):2356-9.
- Valletta E, Fornaro M, Cipolli M, Conte S, Bissolo F, Danchielli C. Celiac disease and obesity: need for nutritional follow-up after diagnosis. Eur J Clin Nutr. 2010 Nov;64(11):1371-2.
- Chandon P, Wansink B. Does food marketing need to make us fat? A review and solutions. Nutr Rev. 2012 Oct;70(10):571-93.
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