Dietitian: Matt Damon says gluten-free diet got him to "high school" weight Actor Matt Damon opened up in a recent interview about how adopting a gluten-free diet helped him lose weight and get down to his "high school" weight. Seeking commentary, including: (1) What are the pros and cons of cutting out gluten with the goal of losing weight? (2) What is your opinion of doing this? (3) What would you recommend for people looking to lose weight?

What are the pros and cons of cutting out gluten for weight loss? Eliminating gluten is essentially an elimination diet—and elimination diets can be valuable diagnostic tools. For some individuals, gluten triggers inflammation, and chronic inflammation contributes to metabolic dysfunction, insulin resistance, and weight retention. Removing that trigger can improve how the body processes and stores energy. The benefit isn't magic in the gluten-free label itself—it's discovering whether gluten is a personal inflammatory trigger. For those with undiagnosed gluten sensitivity, the results can be significant. For others, they're simply eating fewer processed carbohydrates by default, which helps regardless of gluten content. The con: gluten-free products aren't inherently healthier. Many are highly processed with added sugars and starches to improve texture. Swapping regular cookies for gluten-free cookies won't move the needle. What is your opinion of this approach? As a starting point for understanding how your body reacts to certain foods, elimination diets aren't a bad strategy. But for weight loss specifically, there's little evidence that gluten-free eating is superior to any other approach. It falls into food-restrictive eating—one of three diet categories alongside time-restrictive and calorie-restrictive eating. Long-term success depends on adherence, not the specific restriction. What would you recommend for people looking to lose weight? Find the approach you can sustain for years. Focus on protein intake, preserve muscle mass, and address underlying inflammation through whole foods—not packaged gluten-free alternatives. Joshua Lindsley, DO | Board-Certified Emergency & Obesity Medicine Highland Longevity | www.highlandlongevity.com

The loss of weight due to elimination of gluten generally indicates a reduction of calories and not a metabolic effect. Bread, pasta, pastries, and snack foods are eliminated out of the daily consumption, and this can easily lower the overall energy intake by hundreds a day. It can be followed by short term weight loss, particularly in individuals whose diets were majorly based on refined grains. There are also less bloating complaints in some patients that may give an illusion of weight loss in the body despite no change in body composition. Issues arise when they are substituted with gluten free foods. Ready-made gluten free products tend to have increased amounts of sugar and fats in order to replace the texture and taste. The intake of fiber also decreases when whole grains like wheat, barley, and rye are not substituted with beans, oats and vegetables. Reduced fiber will decrease speed of digestion and increase blood sugar fluctuations and this increases difficulty in controlling appetite in the long run. Individuals who are not affected by either celiac disease or gluten sensitivity do not really have any definite health benefit of gluten alone elimination. Protein consumption, fiber content, sleep and regularity are all that sustain weight loss. The elimination of gluten can be a helpful reset button to the highly processed diet but rarely brings sustained change unless the entire eating habit undergoes a change as well.

1. The biggest pro of a gluten-free diet is the reduction in inflammation it can provide, especially for individuals with celiac disease or gluten sensitivity. Gut inflammation can contribute to symptoms like fatigue and brain fog, which can make it harder to find the energy and consistency needed for physical activity. The main con is that gluten-free alternatives are not necessarily healthier. Gluten often functions as a binder, and without it, manufacturers may add more sugars, starches, or additives to improve taste and texture. As a result, some gluten-free products can be higher in calories than their gluten-containing counterparts, which can make weight loss more difficult. 2. Weight loss occurs when your body uses more calories than you consume. When you are in a calorie deficit, your body draws on stored energy, including body fat, to meet its needs. A gluten-free diet will not directly result in weight loss if total calorie intake remains higher than what your body needs. It's possible that Matt Damon was sensitive to gluten, and that eliminating it helped him feel better overall, which made him more motivated to exercise. It is also likely that he replaced many gluten-containing foods (often refined grains and baked goods) with lower-calorie, higher-protein, or more nutrient-dense options. If that shift put him into a consistent calorie deficit, his body would tap into fat stores over time, resulting in weight loss. 3. There are two options I recommend for people looking to lose weight. The first method involves more math and tracking, but it is generally more effective. Use an online calculator to estimate your TDEE (total daily energy expenditure), which is the number of calories you need to maintain your current weight. Subtract 500 calories from that number to set a daily target. Over a week, that creates roughly a 3,500-calorie deficit, which approximately one pound of weight loss per week. The second method is simpler and does not require calorie counting but involves more guesswork. Reduce the amount of food you're already eating by about 20% to lower your overall calorie intake. Combine this with 7,000 to 10,000 steps per day, and you'll be on the right track for consistent weight loss.

Some of patients say they went gluten free and the scale dropped. For a movie role, strict rules feel easier. Many also cut bread, pasta, and desserts, so calories drop. That drives the change, not gluten as a hormone. Gluten free snack foods can be low in fiber and easy to overeat. Without celiac disease or true wheat sensitivity, I rarely recommend it. I found a study of 165 adults followed for 12 months. A 4:3 fasting plan produced 7.6% weight loss versus 5% with daily calorie restriction, and fewer dropouts, 19% versus 30%. Another paper reported vitamin B12 deficiency at 12.3% on a gluten free diet versus 1.6% in controls. My advice is simple. Protein, plants, and strength training. Sleep. Walk daily.

(1) Cutting out gluten might aid weight loss for some people, but it's not a guaranteed solution. A pro is that it could encourage healthier eating habits if it leads to reducing processed foods like pastries and snacks. However, a con is that many gluten-free products can be just as calorie-dense and less nutritious, potentially undermining weight loss goals if not chosen carefully. Eliminating gluten unnecessarily might also lead to missing out on important nutrients if the diet becomes too restrictive. (2) Personally, I think going gluten-free solely for weight loss isn't the most effective approach unless there's a medical need, such as celiac disease or gluten sensitivity. It often shifts focus from sustainable, balanced eating practices to the exclusion of a single nutrient, which can feel restrictive and unsupportive in the long term. (3) For sustainable weight loss, I recommend focusing on balanced nutrition with plenty of whole, minimally processed foods, alongside regular physical activity. Tracking portion sizes and paying attention to how certain foods make you feel can also help. Finding a routine that's enjoyable and fits your lifestyle is key to consistency and long-term success.

From the standpoint of behavioral health and neuropsychology, dietary habits and behavior are more important for long-term weight loss than removing a particular nutrient. There is no proof that avoiding gluten causes metabolic weight loss in healthy people or that gluten itself causes weight gain (Freeman et al., 2017; Xin et al., 2023). People who follow a gluten-free diet usually lose weight because they consume fewer processed foods and fewer calories, not because they avoid gluten in general (Kim et al., 2017). Sustainability is a drawback of strict elimination diets. Dietary restriction increases activation in reward and attention-related brain regions, such as the putamen, orbitofrontal cortex, and anterior cingulate cortex, according to neuroimaging research, making restricted foods more noticeable and difficult to avoid (Stice et al., 2013). Rebound eating is more likely as a result of this increased reward response, especially when under stress or experiencing negative emotions (Casari et al., 2025). Strict regulations frequently have negative behavioral effects over time. Caution should also be exercised when attempting to return to a "high school weight." Age affects muscle mass, body composition, and metabolic requirements. It is not always healthy or appropriate to maintain or return to adolescent weight in later adulthood (Willett et al., 1999). According to research, when predicting cardiometabolic risk, current weight status and health behaviors are more important than past weight targets (Zhao et al., 2020). The best strategy for people trying to lose weight is one that is age-appropriate, flexible, and sustainable. Since adherence and consistency are the best indicators of long-term success, current guidelines prioritize overall dietary patterns, such as Mediterranean or DASH-style eating, over single-nutrient elimination (Lavie et al., 2018; Curawski & Bartosiewicz, 2025). From a behavioral and neuropsychological standpoint, long-term health is built on sustainable habits rather than restrictions.

(1) What are the pros and cons of cutting out gluten with the goal of losing weight? The main reason some people lose weight on a gluten-free diet has less to do with gluten itself and more to do with what they stop eating. Many gluten-containing foods are highly processed and calorie dense, so removing them can naturally reduce overall calorie intake and improve food quality. Some people also experience less bloating, which can feel like weight loss even if fat loss is modest. On the downside, gluten is not inherently fattening, and cutting it out unnecessarily can limit whole grains that support digestion, heart health, and satiety. Many gluten-free products are actually higher in sugar and fat to compensate for texture and taste. This can stall progress or even lead to weight gain if portions are not managed. There is also a sustainability issue. Eliminating gluten without medical need can make social eating harder and increase food anxiety. For long-term weight management, overly restrictive diets often backfire once normal eating resumes. (2) What is your opinion of doing this? As a dietitian, I see gluten-free diets as a tool, not a solution. For people with celiac disease or true gluten sensitivity, it is essential and often improves overall health and energy. For everyone else, weight loss usually comes from increased awareness and reduced processed food intake rather than the absence of gluten itself. If someone like Matt Damon found success, it likely worked because the diet helped him simplify his choices and stay consistent. That does not mean gluten was the problem, but rather that structure and discipline were. Different people respond to different frameworks. I generally caution against framing gluten as the villain. Weight loss success should be built on habits that can be maintained for years, not short-term eliminations driven by celebrity anecdotes. (3) What would you recommend for people looking to lose weight? I recommend starting with consistency rather than restriction. Focus on eating mostly whole foods, prioritizing protein and fiber, and creating meals that keep you full. This approach naturally reduces calorie intake without needing to ban specific food groups. Strength training, daily movement, and adequate sleep are just as important as diet. Many people overlook stress and sleep, which strongly influence hunger hormones and fat storage. Weight loss becomes much harder when recovery is ignored.

Going gluten-free can lead to weight loss for some people, but not because gluten itself is fattening. The pros are mostly behavioral: cutting gluten often removes highly processed foods like pastries, pizza, and refined breads, which can naturally reduce calories and improve blood sugar control. For people with celiac disease or non-celiac gluten sensitivity, going gluten-free can also reduce inflammation, bloating, and GI discomfort, which may make eating and training feel easier. The cons are real, though. A gluten-free diet isn't automatically healthier, many gluten-free packaged foods are lower in fiber and higher in sugar or fat. Cutting out whole grains can also mean missing nutrients like B vitamins and iron. For weight loss, gluten-free can become unnecessarily restrictive and harder to sustain if there's no medical reason for it. My take: if someone loses weight going gluten-free, it's usually because they simplified their diet and reduced ultra-processed carbs, not because gluten was the problem. For most people trying to lose weight, I recommend focusing on fundamentals instead: protein at every meal, more vegetables and fiber, fewer liquid calories, consistent movement, and better sleep. If gluten-containing foods trigger symptoms or lead to overeating, reducing them can help, but it's not a requirement for fat loss. People don't lose weight because they cut gluten, they lose weight because they cut processed food and eat more intentionally.

(1) Cutting out gluten can lead to weight loss for some people, but usually not for the reasons they expect. When someone drops gluten, they often end up cutting back on a lot of processed foods--breads, pastas, pastries--that are easy to overeat. That alone can trim calories. But losing weight isn't a built-in outcome of going gluten-free. Many gluten-free substitutes are just as high in sugar and refined starches, so the swap doesn't automatically make a diet healthier. In most cases I've seen, the people who lose weight on a gluten-free plan are the ones who shift toward more whole foods, not because gluten was the thing holding them back. (2) If a person has celiac disease or a real gluten sensitivity, avoiding gluten is essential. Outside of that, I don't usually suggest cutting it purely for weight loss. It can create restrictions that aren't necessary, and some folks end up relying heavily on pricey gluten-free packaged foods that don't offer much nutritionally. Still, if someone notices they feel better or more intentional about their eating when they avoid gluten, that awareness can be helpful. (3) For most people, steady weight loss comes from small habits that feel doable every day--getting enough fiber and protein, staying hydrated, and keeping ultra-processed foods in check. Paying attention to patterns rather than jumping on trends tends to make the process smoother. And I always encourage people to track how their energy, digestion, and overall health are shifting, not just what the scale says.

Hi, I hope you are doing well. My name is Kristy Thomas, a registered nutritionist at Prowise Healthcare with 4 years of experience in health and wellness. Here are my insights on Matt Damon's comments about following a gluten-free diet for weight loss. (1) What are the pros and cons of cutting out gluten with the goal of losing weight? In some cases, eliminating gluten can lead to weight loss. For many people, this is as simple as cutting out a few processed foods, such as pastries, bread, and pizza, which can improve calorie consumption, promote better digestion, and be beneficial for those sensitive to gluten. Although gluten is not a substance that is inherently fattening. Just cutting gluten out is unlikely to improve anyone's health as many gluten-free options are available that are processed and can be high in calories, sugars, and fats. Furthermore, cutting gluten out can negatively affect a person's fiber consumption and that is essential for one's digestive health and the feeling of fullness in a person. (2) What is your opinion of doing this? A person can have a gluten-free diet if they have coeliac disease or some other version of gluten intolerance, as a gluten-free diet can be a health benefit. Just having a gluten-free diet in and of itself is not going to be beneficial to a person's overall health, especially for weight loss. While the consumption of gluten can be a major part of a person's diet, the focus of the diet really should be on other more important factors, like how much you eat, the quality of foods you are eating, and how you are living or your lifestyle. (3) What would you recommend for people looking to lose weight? The best approach for you is simple and balanced. Your focus should be on eating nutrient-dense foods like vegetables, fruits, legumes, healthy proteins, whole grain carbs, and healthy fats. Being more physically active, sleeping better, and being consistent are all more important to your health and well-being than cutting out a single ingredient. For dieting, the focus should be on achieving long-term health, not the short-term quick fixes that celebrities are using. Please feel free to contact me if you need any additional insights. Thanks & Regards Kristy Thomas, Registered Nutritionist, Prowise Healthcare Website: https://prowisehealthcare.com Email: kristy@prowisehealthcare.com