Published April 30, 2026 02:45PM<\/p>\n<\/div>\n Key Takeaways<\/strong>: A recent study published in Nature Health\u00a0<\/em>used AI to analyze 400,000 Reddit posts mentioning GLP-1 medications such as Ozempic and Wegovy. The researchers found that nearly 70,000 Redditors reported taking GLP-1s. Of those people, some experienced side effects not observed in clinical trials, specifically body temperature and hormonal\/menstrual disruptions. The lead researcher of the study and doctors share how these side effects can interfere with exercise and how to adjust your training when taking a GLP-1 medication.<\/p>\n <\/section>\n With any medication, the official label spells out the laundry list of risks pulled from clinical trials. But controlled studies don\u2019t always reflect how a drug is experienced in the real world. When it comes to GLP-1 drugs like Ozempic, Wegovy, and Zepbound, there are growing anecdotal reports on social media of less-recognized symptoms, according to a recent study published in Nature Health<\/i><\/a>. We interviewed the lead author of the study and doctors to find out whether these previously unknown side effects can affect performance and how to adjust your workouts when taking a GLP-1.<\/p>\n Using AI, the study researchers analyzed more than 400,000 Reddit posts written by people who mentioned GLP-1s. Upon reviewing those 400,000 posts, nearly 70,000 people reported taking a GLP-1 medication (semaglutide or tirzepatide); the posts analyzed were dated between May 2019 and June 2025. Alongside well-established side effects like nausea, fatigue, and constipation, researchers found that nearly four percent of Reddit users also described hot flashes, chills, fever, and menstrual changes like irregular or unusually heavy bleeding.<\/p>\n \u201cWe can\u2019t say for certain whether these drugs are causing menstrual irregularities or temperature regulation issues,\u201d Neil Seghal<\/a>, lead author of the study, tells Outside<\/i>. Rather, the social media reports suggest there may be other side effects that researchers should be looking at based on real-world use because the way people are using GLP-1s\u2014microdosing them or using compounded formulations\u2014diverges from how they\u2019re used in clinical trials, he says.<\/p>\n Of course, anecdotal data (particularly from self-reported, anonymous forums like Reddit) comes with limitations. People may have other underlying health conditions or lifestyle factors that explain their symptoms independently of the medication itself. For instance, \u201ca woman who is in perimenopause or menopause could experience hot flashes because of estrogen depletion,\u201d Dr. Yuval Pinto<\/a>, an obesity medicine physician at Johns Hopkins Medicine, tells Outside.<\/em><\/p>\n Still, there are a few biologically plausible explanations for why these patterns may show up. For one, rapid weight loss (whether from medication, diet, or other lifestyle habits)\u00a0is known to temporarily disrupt hormonal levels. In regard to thermoregulation, which refers to the body\u2019s ability to control its temperature, by losing body fat, \u201cyou\u2019re losing insulation, so thereby it follows that you\u2019re less tolerant to the cold,\u201d says Dr. Nora Lansen<\/a>, board-certified family physician and chief medical officer of Elektra Health, a women\u2019s telemedicine service.<\/p>\n Those shifts aren\u2019t just uncomfortable, though. For physically active users, they may subtly affect\u00a0recovery, endurance, and performance over time.<\/p>\n Even outside the context of GLP-1s, disruptions in temperature regulation and menstrual function can make exercise feel harder than usual. Take hot flashes\u2014those spontaneous waves of warmth<\/a> that typically flood the chest, neck, and face, and are followed by sweating. Beyond discomfort, they\u2019re also commonly accompanied by fatigue, dizziness, and nausea, all of which can make it more difficult to sustain longer or higher-intensity efforts. Staying hot for too long during exercise can also cause fainting. This is especially relevant if you\u2019re running or hiking in the outdoors on a hot day.<\/p>\n Existing research<\/a> shows that menstrual changes (like heavier bleeding) can increase iron loss, which plays an important role in transporting oxygen and energy production. Over time, low iron levels can make someone feel more winded, less powerful<\/a>, or generally \u201coff\u201d during workouts. If you\u2019re feeling dizzy or less alert, this can make navigating the outdoors potentially dangerous. So, it\u2019s crucial to listen to your body, whether you\u2019re at the gym or on the trail.<\/p>\n Layer known GLP-1 side effects on top of body temp and menstrual\/hormonal changes, and the effects on athletic performance compound. Remember, \u201cmany patients on a GLP-1 are under-eating and slightly dehydrated,\u201d says Dr. Hector Perez<\/a>, a bariatric surgeon and internal medicine physician at Montefiore Medical Group in Bronx, New York, tells Outside<\/em>. Sometimes,\u00a0how much a person drinks or eats while\u00a0on a GLP-1 is dramatic, which impairs their temperature regulation, Perez says. Not consuming enough nutrients and water also leaves the body without sufficient fuel for training and recovery.<\/p>\n Here are some tricks to make training more accessible even when the body is going through changes associated with GLP-1s.<\/p>\n Resistance training remains one of the best ways to maintain muscle<\/a> during weight loss, says Lansen. There\u2019s even evidence to support that it may ease hormone-related symptoms<\/a> like hot flashes, too.<\/p>\n However, high-intensity workouts can add stress to a body that\u2019s already running on low energy, on top of adjusting to dizziness, fatigue, or extreme temperature swings. While you don\u2019t have to skip movement altogether, it\u2019s important to, at the very least, start with a gentle warmup, says Dr. Sarah Eby<\/a>, a sports medicine physician at Mass General Brigham and assistant professor of physical medicine and rehabilitation at Harvard Medical School. \u201cAnd extend it longer than you usually would if you\u2019re experiencing chills from a medication.\u201d<\/p>\n Instead of pushing through an unusually difficult HIIT workout, Eby suggests lower-intensity options like incline walking, cycling at a conversational pace, or strength training with higher reps and lower weights. She says yoga is a great option, too.<\/p>\n If your internal thermostat feels off, your surroundings matter more than usual.<\/p>\n \u201cExercise in cooler temperatures, whether that\u2019s earlier in the morning or indoors in an air-conditioned environment,\u201d\u00a0Eby recommends to anyone prone to overheating or hot flashes. \u201cAlso have cold water by your side and make sure to stay out of the sun.\u201d And Pinto suggests working out near a fan if possible.<\/p>\n GLP-1s can blunt appetite and thirst cues, making it easy to unintentionally under-hydrate.<\/p>\n A general baseline (eight to 12 cups of water each day) is a good starting point, though \u201cadding sodium\u2014either through food or a simple electrolyte mix\u2014helps retain fluid and improves dizziness and chills,\u201d Perez says. But because GLP-1s in particular also make you feel full quickly, \u201cspacing fluids away from meals can help,\u201d he adds. \u201cSmall, frequent sips throughout the day are often better tolerated than large volumes at once.\u201d<\/p>\n \u201cTraining fasted or under-fueled can worsen that shaky, flushed feeling,\u201d Perez says, which is why a pre-workout snack goes a long way. Look for easy-to-tolerate combinations of carbs and protein\u2014yogurt with fruit, half a banana with peanut butter, or a handful of nuts. It doesn\u2019t have to be a full meal; it just has to give your body something to work with.<\/p>\n Usually, that drop in energy or that \u201cwhy does this suddenly feel so hard?\u201d moment is a frustrating yet common part of adjusting to a GLP-1, Pinto says. He encourages people to take it easy and give themselves time to adjust, whether that involves pulling back temporarily or redefining what a \u201cgood\u201d workout looks like right now. \u201cAny movement is a blessing,\u201d he says, noting that the best, most fulfilling routine is the one you enjoy.<\/p>\n Want more\u00a0Outside<\/i>\u00a0health stories?\u00a0Sign up for the Bodywork newsletter<\/a>.<\/strong><\/p>\n <\/div>\nWhat GLP-1 Side Effects Did Redditors Report?<\/h2>\n
How Can GLP-1 Body Temperature and Hormonal Changes Impact Your Workouts and Outdoor Adventures?<\/h2>\n
How to Adjust Your Training When Taking a GLP-1 (Without Quitting Altogether)<\/h2>\n
1. Pull Back on Intensity When Symptoms Flare<\/h3>\n
2. Be Strategic About Where and When You Exercise<\/h3>\n
3. Hydrate Proactively, Not Reactively<\/h3>\n
4. Remember to Fuel\u2014Even When You\u2019re Not That Hungry<\/h3>\n