Catherine Tanaka
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Why Women 40+ Gain Weight Despite Unchanged Eating Habits

Fat Loss and Fitness over 40 for women can be a puzzling phenomenon of unexplained weight gain despite an unchanged diet. It can be incredibly disheartening to step on the scale and see the numbers creeping up, even when you feel like you're sticking to your usual eating habits, that you're doing the workouts and trying really hard. If you can relate, you're not alone!  I meet women every day entering midlife that suddenly struggle with peri-menopause weight gain.

This blog post delves into the frustration of weight gain when your diet remains seemingly unchanged. We'll explore some possible factors and shed light on the various underlying causes that may be at play. While weight gain is a complex issue with many factors, understanding the potential reasons behind it can help you make informed choices and take proactive steps toward maintaining a healthy weight.

4 Reasons for Your Unexplained Weight Gain 

We will explore four potential reasons for your weight gain, even when you haven't changed your diet or exercise routine significantly. 

1. Aging Gracefully

The beauty of getting older is that there is so much wisdom and experience that we can tap into and hopefully a greater sense of self and self confidence.  The challenge is often that our hormones shift impacting our energy leaving us with lower energy levels, digestive discomfort, weight gain, and even new aches and pains.

Aging can result in hormonal changes for both men and women.  Today we are focusing on women since that's who I specialize in supporting.  These hormonal changes in women can contribute to the loss of some lean muscle mass and increases and changes in fat storage in our bodies.

The great news is that there is so much that you can do about it to be able to age gracefully through these years.

2. Hormones

Your thyroid is the master controller of your metabolism and can greatly contribute to your weight gain over 40 in women.  Several things can affect it and throw it off course.

Your metabolism slows down when your thyroid gets off course and produces fewer hormones.  And when your metabolism slows down, you can gain weight.  This proves to be especially true if you have a history of slashing calories low or if you're in a perpetual state of dieting with a low calorie diet of 1500 calories or lower.  And sometime, even though you're eating the same way you always have, the natural progression of muscle loss in women greater compound the effects of hormones on fat retention and related changes.

Pro Tip: Find a functional nutritionist (I'm getting my certification as we speak so hang tight) or your naturopath to get you hormones tested with a blood test and a dutch test.  Also,  try the thyroid-supporting recipe I created for you at the end of this post.

3. Sleep

There is plenty of research that shows the influence that sleep has on your metabolic rate.  And as we age, getting a good night's sleep can become harder and harder- but more than that our systems become more sensitive to the stressors in life. And not getting adequate sleep regularly is a big stressor on our systems and metabolism as we approach our 40's into our 50's.  

Sleeping enough is a natural fat loss hack! 

The general consensus is to get 7-9 hours of sleep every night to help avoid weight gain. In addition to this, if you're finding that you're needing 9+ hours of sleep this is an indication that you might be deficient in a nutrients or that there is an underlying health condition to consider. 

Pro Tip: Get at least 7 hours of sleep every night.  The first place to start is by implementing proper sleep hygiene.

4. Stress

It seems to be everywhere!  So many things that can cause stress responses in your body.

And being in a perpetual state of feeling stressed, even perception alone, or having the relentless need to be busy and never rest increases your stress hormones which is a big way that women in midlife get stuck with extra body fat.

While you can't necessarily change your stressors, you can try to adjust your stress response to them.  This is where I use mindset, mindfulness and meditation along with other tools to support my clients in managing their stress levels

Pro Tip:  Try meditation or yoga.  Or even mindful eating.  Even those new adult colouring books that are all the rage now?


Understanding why you have an unexplained weight gain despite an unchanged diet empowers you to take proactive steps towards the cause. As we get into our midlife, over 40 for women, things like aging, hormones, stress, and sleep are interconnected and can all contribute to weight gain, even if you're eating the same way you always have.

Recipe (Thyroid friendly)
Seaweed Sushi Bowl

Serves 2

  • 1 cup cooked rice
  • 1 avocado (thinly sliced)
  • ½ cucumber (diced)
  • ½ red pepper (thinly sliced)
  • 1 green onion (chopped)
  • 2 tablespoons dried seaweed (arame, wakame, or crumbled nori sheets)
  • 2 tablespoons sesame seeds
  • 3 tablespoons rice vinegar
  • 3 tablespoons gluten-free tamari sauce
  • 1 tablespoon lemon juice
  • 1 tablespoon sesame oil
  • ½ garlic clove
  • dash salt and pepper

Split the first seven ingredients into two bowls.

Mix the rest of the ingredients together to make the dressing.

Pour the dressing over the sushi bowls.

Serve & Enjoy!

Tip:  This is a great lunch to take on the go.  Keep dressing in a separate container so you can give it a shake before adding it to the sushi bowl.

About the Author Catherine Tanaka

My name is Catherine Tanaka. I am a Personal Trainer, Transformation Coach, Yogi enthusiast and Mom of two. I am on a mission to make a difference in others happiness through fitness using the best research available to give you the best fitness hacks to make being the best version of you possible. Learn more about my one-on-one coaching or check out my Online Course - The Body Project Protocol.