How Your Body Changes When You Start Exercising

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When you first start an exercise regimen, it can take a lot of energy to keep it up, especially after the first couple of days. You may experience soreness, fatigue, hunger—even weight gain—all of which can zap your motivation. But these effects are usually short-lived. If you maintain your exercise program, typically what you’ll find is your body changes in more positive ways, which can improve your health, increase your quality of life, and motivate you to keep going.

Exercise Effects

Often, what feels like negative side effects of exercise are your body’s way of adjusting to a workout, and telling you what it needs.

  • Soreness. Muscles that are a little tired and sore after a workout mean your regimen is working. Your muscle cells, which sustain damage during exercise, are repairing and remodeling, and getting stronger. You may feel the most soreness 24 to 48 hours after a workout (called delayed onset muscle soreness or DOMS). This should go away within 3 to 4 days. If it doesn’t, or if you feel pain after a workout, talk to your doctor. You can also take a short walk or do a light activity like swimming after your workout to help minimize the soreness. Sit in the sauna for 20 minutes if you’re at a gym with one.

  • Fatigue. Different from physical exhaustion after an intense workout, fatigue is what you may feel (or perceive) during or in between workouts. Fatigue actually protects you from overexertion. It’s also what causes many people to skip their workout or cut it short. You can combat fatigue by getting plenty of sleep and eating healthy carbohydrates, such as bananas, sweet potatoes and beans. You should also drink plenty of water before, during and after exercise to strengthen the flow of blood to your muscles. Rest in between workouts, and work different muscle groups on different days. With the right self-care, exercise should leave your body feeling less tired and more energized.

  • Short-term weight gain. Exercise puts stress on your muscle fibers, causing small tears and inflammation. Your body is also storing more glycogen (sugar your muscle cells convert to glucose for energy). Both of these can lead to water retention and cause weight gain after exercise. If you notice the scale going up, don’t be alarmed. The weight will start to come down after a few weeks as your muscles adjust to your new routine.

  • Hunger. Many people find their appetite increases with exercise. Though the research is not clear on exercise’s effect on hunger, you may be taking in more calories than you’re burning. Take a timeout to consider if you’re actually hungry or eating for other reasons, such as boredom, stress or other factors. Stick with low-calorie, high protein and high-fiber foods that fill you up, such as beans, vegetables, low-fat dairy, and lean meats.

Benefits of Exercise

When it comes to exercise, the more you stick with the program, the better your body—and mind—will feel. 

  • More energy. One of the most helpful effects of exercise is that, in general, you have more energy. Your body benefits from greater muscle strength and a more efficient cardiovascular system, thanks to increased oxygen and nutrients that go right to your body tissues. This helps boost endurance and makes it easier to tackle your daily to do list.

  • Improved heart health. Exercise is also good for your heart. The increased blood flow raises the oxygen levels in your body, improving circulation and lowering your risk of heart disease. Studies show that regular exercise also lowers your blood pressure and triglyceride levels.

  • Weight loss. Both aerobic activity and strength training play key roles in helping you control your weight with exercise. As you burn energy and gain more muscle, your body begins to burn off more calories (muscle burns more calories compared to fat). This effectively speeds up your metabolism, making it easier to drop those pounds, and keep them off.

  • Clearer thinking. Research suggests that regular strength training and aerobic exercise may also help improve thinking and learning skills. Strength training provides an opportunity to overcome obstacles in a controlled, predictable environment, increasing mental resilience.

  • Better mood. During exercise, your body releases chemicals that can help improve your mood and make you feel more relaxed. This can help you handle everyday challenges more effectively, and help you manage stress, anxiety and depression.

If you’re struggling to get an exercise routine off the ground or you’re losing your motivation, try to stay focused on the long-term benefits. With determination and commitment, your hard work will pay off in a relatively short amount of time. Also, remember to check with your doctor if you have been inactive for a while, or have a chronic health condition or other fitness concerns.

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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2020 Jan 20
  1. How Long Does it Really Take to See Fitness Results? U.S. News & World Report.
  2. Exercise: 7 benefits of regular physical activity. Mayo Clinic.
  3. Benefits of Exercise. Medline Plus, U.S. National Library of Medicine.
  4. 18 Reasons to Exercise. Psychology Today.
  5. How Sore Should You Be After a Workout? U.S. News & World Report.
  6. Ament W, Verkerke GJ. Exercise and fatigue. Sports Med. 2009;39(5):389-422. doi: 10.2165/00007256-200939050-00005.
  7. Tips for Avoiding Muscle Fatigue When Exercising. Hospital for Special Surgery.
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