As a fitness professional I get asked this question a lot. You work so hard in the gym and you can’t figure out, why the scale sometimes doesn’t do the justice to the workout you just did. Either you just did fasted sweaty cardio session or lift all the weights in the gym, you are still heavier than you were before the workout. Doesn’t make sense, right? Let’s look at what actually happens to your body, when you work out. Does it make a difference, if you do cardio or strength train? Will HIIT make you lighter after the work out?


DURING THE WORKOUT. Within first 10 minutes of your workout, you will notice increase in your heart rate. This instantly brings more blood to your brain, making you more alert. With stress endorphins are released. They decrease feeling of pain, lead to feeling of euphoria, modulation of appetite and enhance the immune response. Think of endorphins as natural morphine. They interact with the same opiate receptors in the brain to reduce our perception of pain. The big difference though is the activation of the opiate receptors by the body’s endorphins, which does not lead to addiction or dependence like morphine does.

Depending on the intensity and duration of your workout, your body will use different energy systems, to keep you going. Blood transfers from your liver and digestive system to skeletal muscles (up to 20 times more blood), slowing down your digestion. Hormones tell the body to convert fat into glucose. Glucose is the sugar body stores from foods we eat in the form of glycogen. Your body uses adenosine triphosphate (ATP), but it only has small stores of both, glucose and ATP, so after it runs out of it, it will require extra oxygen to create more ATP. More blood is pumped to the exercising muscles to deliver additional oxygen. Without enough oxygen, lactic acid will form instead. Muscles generate lactic-acid as a byproduct of intense exercise. As lactic acid builds up, your pH of the blood around muscles drops, which causes fatigue and prevents you from continuing to exercise. You know that burn you feel? That’s a sign your muscles need to stop contracting to effectively metabolize build-up of lactic acid. Your diaphragm is a hard worker as well. It can pull in 15 times more oxygen than at rest.


RIGHT AFTER THE WORKOUT. One of the biggest factors in weight gain immediately after the workout is fluid retention. If you lose 4oz of sweat per workout and drink 20oz of fluids, you will have excess of 16oz in you. Eventually, if you are not dehydrated, your body will get rid of the access water, but it might not happen right after you stop working out. Another cause of water retention can be dehydration too. If you don’t drink enough fluids, your body will trigger survival mechanism and retain the fluids you already have in your body. But all that should go away, within the next few days. And then there is DOMS. Delayed onset muscle soreness. It is soreness you feel 24-48 hours after you workout. During the workout, you tear your muscles, which is necessary in muscle growth process. Those little tears in your muscle fibers can cause slight swelling, resulting in water retention within the muscle. Immediately after the workout your body will try to get to a resting state as quickly as possible. The fitter you get the faster this process is. All the body functions that slowed down during the workout, will now speed up (including your digestion) and vice versa. Interestingly, during this process there is typically an over-reaching effect, where the body doesn’t just go back to “normal” pre-exercise levels, but it actually overcompensates. For example, when you exercise your heart activity is elevated as well as resistance within the blood vessels, which results in increased blood pressure. However, after the workout some people can experience “post-workout hypotension” (low blood pressure). 


FEW WEEKS AFTER STARTING REGULAR EXERCISE. Over the next few weeks, you’ll slowly start to build up production of mitochondria via a process called mitochondrial biogenesis. Mitochondria are the parts of your cells that convert carbs, fat, and protein into fuel that your muscles use to do their job. After six to eight weeks you can increase your mitochondria by up to 50%. With more mitochondria in your cells, you’ll start to feel fitter and your endurance will increase. This means running three miles, will no longer feel as difficult as it did during that first week. It takes about 2 weeks to start seeing some results, if you follow a healthy nutrition plan. But since we are all very unique, some people might see it before others. After one year of regular exercise, your bones will be denser, which reduces your risk of osteoporosis. In fact, researchers have shown that regular resistance training, when combined with aerobic exercise, can actually reverse the effects of osteoporosis after 12 months.


Now find that workout routine, that makes you happy and enjoy all the benefits of exercising. And don’t step on the scale immediately after, expecting lower number on the scale 😉.