I'm Karen Avila, a retired wrestler and strength trainer. I help people improve their physical fitness, build strength, and feel more capable in everyday life. My approach centers on practical exercise and nutrition habits that support the things you want to do.
When you start losing weight, it's natural to watch the scale. I also want you to pay attention to how you feel. Do you have the energy to get through your day? Are you moving comfortably? Can you carry your groceries, climb the stairs, and keep doing the activities you enjoy?
I'm not against GLP-1s at all. My concern is that you still need guidance while your appetite, weight, and routines are changing. In this first article, I'll walk you through how these medicines affect your body and why your strength and energy deserve attention along the way.
Let's start with the name. GLP-1 stands for glucagon-like peptide-1, a hormone your body releases in response to eating. It helps regulate appetite and blood sugar. Medicines that activate its receptor work through this signaling system, helping you feel satisfied with less food. They also stimulate insulin release when blood glucose is elevated, reduce glucagon signaling, and can slow stomach emptying. Insulin helps your body use glucose; glucagon signals your liver to release it. These coordinated effects help explain why the medicines influence both food intake and blood-sugar control. Drucker, 2022, Molecular Metabolism
The way I explain the appetite effect is that your body receives a stronger message that you've eaten and have enough for now. You may hear people describe less “food noise,” meaning fewer persistent thoughts about eating. That can be a welcome change. But feeling less hungry doesn't tell you whether you're getting the nourishment you need. A 2025 joint clinical advisory identifies inadequate nutrient intake as a concern during GLP-1 treatment. Mozaffarian et al., 2025, The American Journal of Clinical Nutrition
You probably recognize some of the brand names. Ozempic and Wegovy contain semaglutide; Mounjaro and Zepbound contain tirzepatide. Semaglutide activates the GLP-1 receptor. Tirzepatide activates both GLP-1 and GIP receptors, involving a second hormone-signaling pathway. These products have different approved uses and dosing. Your prescriber can explain which is appropriate for you; tirzepatide's additional action doesn't guarantee that you'll experience fewer side effects. Wegovy prescribing information; Zepbound prescribing information
The everyday benefits I care about include moving more comfortably, returning to activities you've been avoiding, and feeling more confident as your weight changes. You may notice changes like these, but everyone's experience is different. Your confidence and mental health involve much more than your weight.
There is also research showing benefits beyond weight reduction in specific groups. In the SELECT trial, 17,604 adults aged 45 or older with overweight or obesity, established cardiovascular disease, and no diabetes received semaglutide or placebo. Major cardiovascular events occurred in 6.5% of the semaglutide group and 8.0% of the placebo group over an average follow-up of about 40 months. That is an encouraging finding for the people studied. The benefit you can expect depends on your health and the medicine you take. Lincoff et al., 2023, The New England Journal of Medicine
If your blood-sugar numbers improve, that is another reason to feel encouraged. I do want to be careful with the language, though: a normal result while you're taking medication doesn't establish that diabetes has disappeared. An international consensus defines type 2 diabetes remission, in the usual case, as HbA1c below 6.5% for at least three months without glucose-lowering medication. Even in remission, you still need ongoing monitoring. Riddle et al., 2021, diabetes remission consensus report
Now let's talk about the concern I hear around muscle. When you lose weight, your bathroom scale tells you the total change. It can't tell you how much came from fat, muscle, or other parts of your body.
If you have a DXA body-composition scan, you may see the term “lean mass.” That includes skeletal muscle, but also water, organs, and other nonfat soft tissues. Strength describes your ability to produce force. Physical function concerns tasks such as walking, getting up from a chair, and carrying things. These measures are related, but a change in one doesn't automatically tell us what happened to the others. Cawthon et al., 2022, European Geriatric Medicine
For example, a body-composition substudy of SURMOUNT-1 found that approximately 75% of the weight lost with tirzepatide was fat mass and 25% was lean mass. Those percentages describe the weight lost during the study. They don't mean participants lost a quarter of their original muscle, and they don't predict your individual result. The lean-mass portion includes more than muscle. Participants also received dietary counseling and physical-activity advice, which matters when interpreting the findings. Look et al., 2025, Diabetes, Obesity and Metabolism
A lower lean-mass reading also doesn't automatically mean you've become weaker. In SEMALEAN, a prospective study of people receiving semaglutide, 106 participants completed 12 months of follow-up. Lean mass declined initially and then stabilized, while average handgrip strength improved. The study lacked a randomized control group, so it can't establish that semaglutide caused that improvement or promise the same outcome for you. It does illustrate why we need to assess strength alongside body composition. Alissou et al., 2026, Diabetes, Obesity and Metabolism
As a trainer, I want to know what you can actually do. How does your usual walk feel? How are you managing the stairs? Have you noticed a change in the activities that used to feel comfortable? I encourage you to establish a starting point and pay attention over time. One body-fat reading can't tell your whole story.
If you already exercise, you may notice that a familiar workout feels different after starting treatment or increasing your dose. Nausea, vomiting, diarrhea, constipation, and fatigue are recognized side effects, and gastrointestinal symptoms can be especially noticeable as doses increase. These effects can make activity uncomfortable or interrupt your routine. Wegovy prescribing information; Zepbound prescribing information
One concern I come back to is eating too little when your appetite drops. You might usually arrive at the gym ready to train, then find yourself feeling drained or wanting to go home. Insufficient food and fluid intake can contribute, but we shouldn't automatically blame fatigue on diet or assume it means you're losing muscle. The joint advisory supports looking at nutrition, symptoms, and physical function together during treatment. Mozaffarian et al., 2025
Please contact your healthcare team if you have persistent nausea, repeated vomiting, difficulty keeping fluids down, or weakness that disrupts your daily life. Severe or persistent abdominal pain, especially if it extends toward your back, requires urgent assessment. Low blood sugar is another consideration, particularly if you also take insulin or certain other diabetes medicines. Your prescribing clinician should handle medication adjustments and significant side effects. Zepbound prescribing information
I want you to have support as your weight changes. If you're struggling to eat, losing energy, or noticing changes in strength, bring those concerns to your healthcare team. You don't have to accept feeling depleted as your new routine. The right follow-up schedule depends on your needs and your clinician's guidance. A 2025 multidisciplinary advisory also recommends ongoing nutritional and lifestyle support alongside medication. Mozaffarian et al., 2025
I often hear the idea of waiting until the weight is off to start thinking about strength. My approach is to include strength in the conversation from the beginning, with activity suited to your health and experience. I want you thinking about how you'll stay capable throughout the process.
In Part 2, I'll explore strength training, interval training, and other forms of exercise during GLP-1 treatment. In Part 3, we'll look at diet, protein, other nutrients, and the evidence surrounding supplements. Throughout this series, I want to help you pay attention to how you feel, what you can do, and what support will help you keep doing it.
This article provides general education. Individual medication, nutrition, and exercise decisions should be made with qualified professionals who know your health history.
written with AI assistance; these are my words and I stand behind them.