7 reasons why you're gaining weight even though you exercise

Kicking off a consistent exercise routine can often be a harder task than it gets credit for.

Not only is it a matter of finding the time and setting the habit, but figuring out the who, what and where that works for you can be a big undertaking.

After all, it means figuring out who you’ll work out with (on your own, with a friend or a personal trainer), what sort of exercise suits you (do you prefer yoga or running laps or both?), and where you might get the most out of it (do you like classes at the gym, or would you rather feel the elements with those beach swims or park runs?)

But once you figure it out? Nothing beats that feeling of having successfully integrated your workout routine into your daily life.

This is why stepping on the scales and finding that your weight hasn’t shifted, or worse, that you’ve actually gained weight, can be so confusing.

At a basic level, we all understand that weight gain occurs when we eat more calories than we actually use, which is why it feels almost like a social contract that real exercise should result in real weight loss [1].

So why is it that sometimes exercise results in a female gaining weight while working out, instead of the opposite?

Is it normal to gain weight before losing it?

It is. But luckily this is usually a temporary weight gain, and not a permanent one.

When you start to work out, your body goes through a process that experts call body recomposition.

This is the process by which you gain muscle mass and lose fat mass, altering not just your overall weight, but changing the shape and look of your body [4].

It’s not uncommon to hear the phrase in exercise and weight loss circles that muscle weighs more than fat, and while the statement itself isn't technically true, it is true that muscle mass and fat mass have different volumes.

A pound is a pound, but a pound of muscle is smaller in its density and takes up less space than a pound of body fat.

In other words, while the number on the scales might not be going down, there’s a good chance you’ll feel slimmer and fitter as your body reaps the rewards of your new workout routine.

Why you might be gaining weight while working out

While body recomposition is the main reason you might be experiencing temporary weight gain while you working out, it’s not the only reason.

In fact, there are a number of explanations as to why you might not be getting the results that you want, and these vary from the simple facts of exercise to habits you can adjust to get you feeling your very best.

So, what are some of the reasons why your new exercise program may not be having an impact on your body weight?

1. You're gaining muscle

Sure, this is a matter of that body recomposition we mentioned above, but it bears repeating. Fat mass doesn’t become muscle mass, but rather fat mass is burned off as energy as a part of the muscle-building process.

Lean muscle mass grows through a method of ‘tear and repair’. Exercise causes tiny tears in your muscle fibres that your body then has to heal, causing the muscle tissue not just to grow in size, but to strengthen overall.

Unfortunately, this isn’t a 1:1 equation — your muscle mass doesn’t necessarily develop at the same rate that your fat mass is burned through, nor is your fat mass burned through at the same rate that your muscle mass develops.

As a result, there can be some weight fluctuations across the body as you go on your exercise journey, and it's important to remember that the number on the scales doesn’t necessarily reflect the changes to your body or your overall health.

2. You're consuming too many calories

Crucial to any positive lifestyle change is a healthy diet that avoids processed foods and unhealthy snacks.

If you don’t adjust your diet and calorie intake to support your exercise, you’ll reduce the impact of your workout [2].

It’s important to understand too that as you lose weight, your metabolism can slow down, particularly if you’re losing a significant amount of weight [3], and regaining that lost weight does not restore your metabolism back to its pre-weight loss levels.

As a result, your caloric intake often needs to be reduced in order to sustain that weight loss and keep your healthy body looking and feeling its best.   

3. You're not doing the right type of exercise program

While studies have found that all exercise should lead to modest weight loss, high-amount/vigorous-intensity groups were found to lose significantly more body mass and fat mass than the low-amount/moderate-intensity group [2].

Aerobic exercise in particular is found to specifically decrease fat mass [4], however, a combination of both aerobic exercise and weight training concurrently is usually most effective in optimising body composition. 

In other words, keep up those park runs, but mix in a little pilates when you can.

4. You're exercising too much

While there is a lot of debate about how much exercise needs to be done at a minimum to maintain a healthy lifestyle and prevent weight gain, too rarely do we talk about the flip side of how much exercise might be too much.

Recent studies have set to rectify this, with one finding that vigorous and high-intensity workouts can actually see your weight plateau or even lead you to put weight back on.

How? Well, it looks like high-intensity exercise can diminish non-exercise physical activity and lower your body temperature.

Put simply: intense exercise exhausts you, which results in lower physical activity across the rest of the day, which, accompanied by a lower body temperature, means you burn less energy ergo fewer calories too [6].

This research indicates that keeping that vigorous aerobic exercise or strength training short and following up with a walk later in the day, may just be the key to seeing that number on the scale drop.

5. You're not resting enough

Speaking of rest, getting enough of it is crucial for our physical, mental and emotional health. In particular, sleep has a deep and multi-faceted relationship with our weight.

Circadian rhythmicity has a significant impact on the weight loss process, and changes in meal timing and sleep disorders both have been found to increase the risk of obesity.

Short sleep duration has also been reported to be associated with higher energy intake, which results in weight gain and an increase in BMI.

In short, not sleeping enough could be the reason you’re not seeing the weight loss you want, and ensuring you get the recommended 7-9 hours a night may just get you looking — and feeling — your best [7].

6. You're not drinking enough water

60% of the human body composition is made of water, meaning that it plays a role in just about every imaginable bodily function. One of those, research indicates, is weight loss.

Being healthily hydrated has been found not just to help your body burn fat, but it’s also likely to naturally suppress your appetite, and stimulate your metabolism by triggering thermogenesis (in other words, those cool glasses of water make your body turn on those internal heaters, burning energy).

It also hydrates your muscle cells and maintains your blood volume during workouts, which increases the benefits of exercise, helps your body remove waste, and may even improve your motivation and reduce stress [5].

7. You're experiencing post-workout muscle inflammation

That tear-and-repair process we mentioned above may not just impact your overall muscle weight gain, but cause you to put on a few pounds as you heal.

Those tiny tears in your muscle fibres do take energy to mend, and as a part of this process, the body retains fluid in order to address the damage.

This can also cause some delayed onset muscle soreness (DOMS), but the good news is that that pain — like this initial weight gain after exercise — is both temporary and usually pretty minor, so try not to take it on board.

Tips for staying motivated (despite the number on the scale)

Feeling like you're gaining weight after working out can be really demotivating and disempowering.

After all, choosing to tackle your health through exercise programs and a healthier diet can be a hard decision to make.

You need the time, support and resources to start that journey, and to feel like you're not seeing the results reflected when you step on the scales can have you veering off course or even giving up. The trick is to stay motivated and not let unwanted weight gain derail you.

But how do you not let the number on the scale affect your commitment to your weight loss goals?

Finding types of exercise that you enjoy

If you hate running laps, try something else, whether that be swimming, a dance class, indoor (or outdoor!) rock climbing, or cycling, there are plenty of different forms of cardio exercise and weight training that you can try out.

Once you find one that makes you feel good, losing fat or building muscle might just become less of the focus than the simple act of going and enjoying yourself.

Get a workout buddy

Do some exercise with people you enjoy spending time with and make it a regular appointment in your shared calendar.

Whether it's a park run with a bestie, reformer pilates with your sister, swimming with a son or daughter, or even PT with a certified personal trainer, finding community around exercise can be a way to not just hold yourself accountable and keep you going, but can also deepen your relationships with more than just your body.

Celebrate non-scale victories

Measure more than just weight, and set other goals.

How long does it take you to run or swim a mile? How long can you hold the plank position in yoga?

Set yourself some achievable goals and track them with a pen and paper, an app on your phone, or your smartwatch. The best part of doing this is planning the rewards for when you hit your targets.

If you're not sure where to start or feel like you need the advice and support of professionals and a community to hit your weight loss goals and not get deterred by any temporary weight gain, a program like Juniper's Weight Reset Programme may be just what you need.

With a mix of medication and guided support from professionals around eating healthy and strength-based exercise, this program can support you in making lifestyle changes that will have you looking and feeling your best.

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