Weight is just a number on the scale and doesn’t tell you about your overall health. At least, not completely. It’s more of a tool you can use to gauge what you’re doing right and where you can improve things a bit.

Though your weight can change (sometimes by the day), sudden weight gain can sometimes indicate an underlying health condition.

Here’s what you need to know so that you can better understand your body and get the help you need to be the healthiest version of you.

Some Weight Gain is Normal

sudden weight gain - daily weight fluctuation

Before we dive into things in earnest, you need to understand one key fact: weight gain happens. In most cases, it’s completely normal and your weight can fluctuate by as many as 10 pounds in just a few days.

So, what causes that weight fluctuation? Well, it’s usually something you ate. Sometimes you might be eating too many calories but not burning enough. In those cases, you should keep an eye on your portion sizes and make sure you are more active throughout the day. If you’re not sure how many calories you should be eating, you can calculate your ideal calorie intake with my FREE female calorie calculator.

Sometimes the weight can be caused by bloating. The reasons for bloating include food allergies (such as lactose and gluten allergies), drinking too much soda, eating a lot of packaged foods, etc.

There are several things you should do to get rid of bloating. First, you should figure out what exactly is the cause. If your problem is food, then you should adjust your diet. If your problem is dehydration, you should drink more water during the day.

Keep in mind that your weight will also change as you get older. The most important thing to remember is you shouldn’t attach your self-worth to your weight.

RELATED POST: 7 Foods That Reduce Bloating

Sudden Unintentional Weight Gain Happens

Unintentional weight gain is different from the standard fluctuations most people see every few days. So, what exactly is it?

It’s when your weight jumps up without any identifiable cause. For example, you won’t be able to trace that change back to the foods you ate or the fact that you didn’t exercise in a couple of days or weeks.

Suddenly, you’re much heavier than you expected even when you haven’t changed a single habit or daily routine.

The Most Common Symptoms of Sudden Weight Gain

sudden weight gain symptoms

There are some symptoms of sudden weight gain which can take more of a toll on your physical health and mental wellbeing.

The most common of these is noticeable changes in your body’s appearance. Often, you’ll notice swelling around your stomach, arms, wrists, fingers, and legs. This swelling can feel uncomfortable and not just because you’re self-conscious about those changes.

It’s because your body isn’t used to the swelling in the first place. Your skin will feel tight and your joints may feel stiff.

There are other symptoms though that can be cause for alarm. These include the following:

  •  Increased heart rate
  •  Difficulty breathing
  •  Fever
  •  Uncontrollable and inexplicable sweating
  •  Sore spots on your skin

If you notice any of these symptoms, you’ll want to contact your doctor as soon as you can. These symptoms are rare, but they’re severe and may indicate a more serious medical issue that only your doctor will be able to diagnose and treat.

RELATED POST: 6 Unexpected Reasons You Can’t Lose Weight

Why Am I Gaining Weight So Fast? – 10 Common Reasons for That Unexpected Weight Increase

reasons for sudden weight gain women

In most cases, sudden weight gain has a cause. The cause varies from person to person but, often, it’s because you’re dealing with some type of medical issue and just don’t know about it yet.

That’s why it’s so important to call your doctor if you notice sudden weight gain in your stomach or other parts of your body. The sooner you can get medical treatment, the easier it will be to get your weight back under control.

Though there are many underlying health conditions that can contribute to weight gain, some are more common for women than others.

1. Underactive Thyroid

Your thyroid is one of the smallest yet most important glands in your entire body. It produces thyroid hormone which helps your body process food into energy and use it appropriately.

When it’s functioning well, it produces the right amount of hormone to help your body use the energy in food to keep you going without gaining weight.

Unfortunately, some people, myself included, experience hypothyroidism. Hypothyroidism means your thyroid isn’t producing hormones at the rate that your body needs. Not only does the condition cause you to put on weight but it can also take a toll on your energy levels.

When your thyroid isn’t producing enough hormone each day, your body can’t use the energy in the food you eat as effectively. This, in turn, causes your body to store those calories as fat.

The more fat you store, the higher your weight climbs.

This condition can cause weight to start building up suddenly and, unfortunately, there’s no easy way to prevent it. The best thing you can do is contact your doctor as soon as you notice any changes in your weight that you can’t explain.

2. Polycystic Ovary Syndrome (PCOS)

Your body relies on the hormones that your ovaries produce to function the way nature intended. If you have PCOS, those hormone levels can be out of whack and contribute to your weight gain and other health issues.

PCOS changes the levels of estrogen and testosterone, the reproductive hormones. This change can result in problems with your menstrual cycle (making your periods irregular or causing you to skip them entirely), migraines, acne and facial hair growth.

PCOS also messes up the way your body uses insulin. This is a problem because insulin is the hormone that turns carbs into energy. When your body develops an insulin resistance, it means that all of the sugars and starches that you eat are stored as fat instead of used as fuels. This then causes the unexpected weight gain.

RELATED POST: How A Hormone Imbalance Can Cause Weight Gain

3. Perimenopause and Menopause

As you age, your hormones change. That means your metabolism can change, too. For most women, these changes happen when they’re older and entering perimenopause and menopause.

This is the period of your life when you stop getting periods and are no longer able to conceive. Both perimenopause and menopause are normal parts of aging, but they can cause you to gain weight unexpectedly.

Your doctor may be able to help you better manage your symptoms and your hormone balance.


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4. Insomnia

I’ve talked about how important a good night’s sleep can be for your overall health before. But did you know that it’s also essential to helping you manage and control your weight?

When you don’t get enough sleep, you need to find other ways to stay energized. For a lot of people, this usually involves a good amount of junk food, energy drinks, and sugar-filled coffees.

And guess what all of those things have in common! They’re all packed with calories! Sure, the caffeine and sugar give you an energy boost, but it’s not enough to help you burn through those extra calories that you’re consuming.

Remember, the more calories you consume and the fewer you burn, the easier it is to gain weight.

Start prioritising sleep each night. Find ways to relax and unwind at the end of the day so you can fall asleep more easily. When you get enough rest, you won’t need to rely on artificial energy sources to help you get through the day.

RELATED POST: How To Have A Healthy Sleep Routine

5. Medications You’re Taking

Unfortunately, some medications can cause sudden weight gain. It’s a side effect that many people just have to deal with. In many instances, medications change your hormones and can cause your body to hold onto fluids more than it otherwise would.

If you’re taking a medication that you believe is causing weight gain, talk to your doctor. They’ll be able to help you strategize a solution or may be able to recommend a different medication that will help you stay at your target weight more easily.

6. Depression, Anxiety and Other Mood Disorders

Your mood can make a huge difference in your weight. If you suffer from depression, anxiety, or any other mood disorder and are experiencing sudden weight gain, don’t wait.

Reach out for help and see if you can identify the main cause of your problems. The sooner you do, the better off you’ll be both mentally and physically.

7. Increased Cortisol Levels

One side effect of today’s way of life is that we are constantly under stress. And any time we are under stress, our bodies produce cortisol.

Cortisol is the body’s stress hormone. However, the constant production of this hormone, even when we aren’t in danger and don’t need to fight or flee can cause health issues, most commonly weight gain.

When there is cortisol in your bloodstream, blood sugar levels are elevated and can stay that way for a long period of time, even days. When your blood sugar is high, you can’t burn through calories easily.

This means that instead, these calories are stored as fat for later use and we gain more weight because of it.

RELATED POST: Is Stress Causing Your Weight Gain?

8. Quitting a Bad Habit

Everyone knows that quitting a bad habit like smoking or drinking excessively leaves you wanting for something to replace that habit with. For many people, the easiest coping mechanism to reach for is food.

The more you eat each day and the less activity you have, the more likely it is that you’ll see a dramatic change in your weight. If you’re struggling with addiction or are trying to break free of the cycle, reach out to your doctor.

They’ll be able to help you find healthier coping mechanisms and may be able to mitigate the amount of weight you gain as you adjust to your new normal.

9. Diabetes

Many people assume that those with diabetes get the disease because of a poor diet or a less-than-active lifestyle. While those can contribute to your risk of diabetes, it’s entirely possible to get a diagnosis when you’re at your ideal weight.

Diabetes forces you to monitor your blood sugar levels and inject yourself with the appropriate amount of insulin to help break down the sugar and convert it into energy. Even if you’re eating healthy foods, your body can end up storing the excess glucose in your blood and end up in your fat stores.

If you’ve recently been diagnosed with diabetes, talk to your doctor and let them know about your concerns.

10. Leptin Resistance

Leptin is a hormone believed to control your body’s ability to lose weight. Your body stores fat as energy for your activities during the day, and leptin is the hormone that tells your body that you’ve stored enough.

It’s that “full” feeling you get when you’ve consumed enough calories. So leptin basically tells your metabolism when to burn calories and when to store them.

If you have leptin resistance, that means that your brain doesn’t get the signals leptin is sending, which can lead to an increase in appetite and a sudden increase in weight. I also have leptin resistance which is why I understand the problems this can cause.

What You Can Do About Sudden Weight Gain

how to deal with sudden weight gain

Ultimately, sudden weight gain is relatively common but that doesn’t mean you can’t do something about it. You just need to be proactive and commit to taking the necessary steps to find a solution.

Think about your lifestyle habits and your diet. Are you exercising enough and doing what you can to be healthy? If so, call your doctor. If not, call your doctor.

Do this even if you think your weight gain is the result of your lifestyle. Remember, they’re in business to help you stay healthy and maintaining a good weight is part of the process.

They’ll be able to answer your questions and make sure you’re not experiencing any of the above medical conditions that could contribute to your weight gain. If you are, they’ll help you find the right treatment so you can start feeling better, fast. 

Love Rachael xx

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Rachael is an Australian born certified personal trainer and nutritionist who holds a Bachelor degree in Science.

After struggling for years to find an exercise and diet program that is tailored to women striving for lean and toned body with no bulk she designed her Lean Legs Program. This program is tailored to each body type and focused on helping women get toned but feminine bodies, without getting bulky.

Her mission is to empower women and help them stay in shape in a healthy and balanced way.

8 Responses

  1. Is this programme effective for older women in perimenopause. I eat totally clean and track my macros . I want to slim my bulky over exercises thighs and lose 1/2 a stone but I am finding it difficult to lose weight.

    1. Hey lovely! Yes, definitely! The workouts in my program are all low-impact so they are suitable for all ages(except minors) and even beginners. It will not only help you slim down your legs but also lose weight overall. I recommend that you give it a try! :)

  2. Hi, what’s the difference between the 3 steps to lean legs and the video course please? Which is best for me starting off with? Or am I best buying the package with both in? I’ve exercised all my life and unfortunately have hit perimenopause and have put on nearly a stone so really need to lose weight and seriously tone up again, and would finally like slim legs. Please help!! Many thanks

    1. Hey lovely ❤️ Let me share more info with you so you can be 100% sure.

      The 3 Steps to Lean Legs Program is an 8-week plan designed to help you get lean and toned without bulking. It consists of a cardio plan, body-weight resistance exercises in the form of photos and short demonstration videos only (that you can watch through the link provided in the ebook), full meal plans (regular and vegan), and separate recipe eBooks.

      The Lean Legs Video Course consists of those same body-weight resistance exercises from the Program but in the form of 12 full-length follow-along videos plus 4 bonus booty workouts, but there are no meal plans, cardio plan, or recipe books.

      If you want both, you may opt for the Lean Legs Bundle which is a package of both products that you can get at a discounted price. Feel free to check out all my programs here. :)

      If you have any questions, don’t hesitate to reach out to us at

  3. Do you have any tips for dealing with bloat? My husband’s family is Asian so Asian foods are a big part of his family life, and also part of our children’s cultural heritage, but those foods, even in small amounts, completely bloat me. Is there anything you can do to combat that? I’m wondering if there’s an ingredient in Asian foods these days that I’m sensitive to. Thank you.

  4. Hey Rachael,
    I noticed that you put sore spots on your skin as a potential cause for unexplained weight gain. I was wondering if you could elaborate on this?
    I get hives from heat, cold, exercise, stress, and anxiety on a daily basis, however I haven’t been able to get diagnosed because all my tests keep returning as normal.

    1. Hi lovely,

      thanks for reaching out! <3

      I'm so sorry that you are experiencing that :( Since Rachael nor I are medical professionals, we cannot elaborate on this subject. It would be best to see your medical professional and he/she can assist you further.

      I do apologize that I cannot assist you further.


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