Some people claim that a gluten-free diet may benefit those who wish to lose weight.
However, there are currently no controlled studies in humans to support this.
Recently, a group of researchers examined the effects of gluten on weight gain in mice. Below is a detailed summary of their findings.
Gluten is a group of proteins found in certain types of cereals, such as wheat, barley and rye. It can trigger celiac disease in people who are gluten intolerant.
Gluten is a major component of the typical Western diet, and is found in bread, pastries, pasta and many types of processed foods.
Some researchers are concerned that it may have adverse health effects, even for people who aren’t gluten intolerant. However, this is a matter of debate.
A number of observational studies have examined the effects of a gluten-free diet on body weight among children and adults with celiac disease.
In general, these studies show that a gluten-free diet may increase weight among underweight or normal-weight celiac disease patients. Conversely, it may cause weight loss among those who are overweight or obese (1, 2).
These observational studies cannot prove causation. When people go on a gluten-free diet, changes in body weight are likely caused by dietary factors other than gluten. Improved calorie absorption and digestive health may also play a role.
Only one previous study, in mice, has investigated the direct effects of gluten on body weight. It showed that following a high-fat diet, containing 4.3% gluten, caused significantly greater gains in weight and fat, compared to a gluten-free diet (6).
This study in mice investigated the effects of a high-fat and standard diet, containing 4.5% gluten, on body weight.
This was a controlled study in mice, examining the effects of a high-gluten diet (4.5%) on body weight, and comparing it with a gluten-free diet.
The mice were assigned to one of four diets, which they followed for 8 weeks:
- Control-Standard Diet (CD): This was a standard, gluten-free, control diet. The authors did not provide any further information on this diet.
- Control-Standard Diet with Gluten (CD-G): This diet contained 4.5% wheat gluten, but was otherwise the same as the CD. The gluten used had been isolated in a laboratory.
- High-Fat Diet (HFD): This was a gluten-free, high-fat diet, based on lard. Its composition is unclear, as the authors did not provide any additional information.
- High-Fat Diet with Gluten (HFD-G): This diet contained 4.5% wheat gluten, but was otherwise the same as the HFD.
The gluten and gluten-free diets were designed to have a similar calorie density and composition. All of the animals had unlimited access to food.
Every week, the researchers measured the mice’s body weight. Calorie intake was also estimated by calculating the difference of food offered and food consumed.
At the end of the study, the animals’ calorie expenditure was assessed by measuring oxygen consumption. To measure gluten absorption and distribution in the body, some of the mice were given radiolabeled gluten.
Finally, the researchers conducted biochemical analyses on the mice’s blood, fat tissue and liver.
Bottom Line: This study examined the effects of a diet rich in gluten on weight gain in mice, and compared it with a gluten-free diet.
Finding 1: Gluten Caused Greater Weight Gain
The mice who consumed gluten gained around 20% more weight than those who were on a gluten-free diet.
Weight gain was accompanied by significant increases in both skin and abdominal fat. In fact, eating gluten caused about 30% greater fat accumulation.
This effect of gluten was stronger among those who were on the high-fat diet, compared to the standard-control diet, as seen in the chart below:
Despite the greater weight gain in the gluten groups, calorie intake remained similar in the gluten-free groups. These findings are confirmed by one previous study conducted by the same research group (6).
Bottom Line: Eating gluten led to significantly greater weight gain, compared to a gluten-free diet.
Finding 2: Gluten Reduced Calories Burned
The mice that got 4.5% gluten in their diet tended to burn less calories in the fasting state between meals, compared to those that didn’t eat any gluten.
Specifically, calorie expenditure decreased significantly in the HFD-G group, compared to the HFD, as seen below:
Conversely, in the CD-G group, calorie expenditure decreased modestly, but the change was not significantly different to the CD group.
This metabolic slowdown might explain why eating gluten promoted weight gain (6).
Bottom Line: The mice who consumed gluten burned less calories, compared to those who were on a gluten-free diet. This may explain why gluten promoted weight gain.
Finding 3: Gluten Was Found in Blood, Fat Tissue and Liver
At the end of the study, the researchers examined the absorption and distribution of gluten in the body by feeding the mice radiolabeled gluten.
They found traces of gluten, or gluten fragments (peptides), in the blood, liver and fat tissue.
Although only tiny amounts of gluten were detected, these findings suggest that gluten, or its peptide fragments, may directly affect the function of these tissues.
In fact, the researchers detected some important changes in certain types of cells in skin fat. For example, they found that levels of UCP1 — a protein that may protect against obesity — were lower in these fat cells.
However, these changes were only significant in the HFD-G group.
Bottom Line: Small amounts of gluten, or its fragments, were detected in the blood, liver and fat tissue. This suggests that gluten may affect these tissues directly.
Before any general claims can be made regarding the effects of gluten on body weight, clinical trials in humans need to confirm the findings.
Also, the mice were fed high amounts of gluten, or 4.5% of their diet. The authors didn’t specify whether this percentage referred to the diets’ weight or calorie content.
Since gluten makes up about 6–18% of wheat’s weight, people who base their diet on wheat products might reach similar intake levels.
However, smaller amounts of gluten might not have any clinically relevant effects.
Finally, the researchers added isolated gluten to the mice’s diet. It is unclear if this isolated form of gluten differs from the gluten naturally found in whole wheat.
Bottom Line: This was a mouse experiment and its results cannot be generalized to humans. For this reason, human studies are needed.
Summary and Real-Life Application
In short, this mouse study showed that eating large amounts of gluten may promote weight gain. But whether these findings can be generalized to humans is unknown.
Nevertheless, as general advice, you should not base your diet on a single type of food. If you tend to eat lots of wheat products, expanding your dietary choices may improve your health.