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Eating the Same but Gaining Weight? This Is Why.

  • Writer: Caylin Goodchild
    Caylin Goodchild
  • Mar 19
  • 2 min read

Have you ever caught yourself thinking:“But I’m eating exactly the same as I used to… so why am I gaining weight?”

You’re not imagining it—and you’re definitely not alone.

 

Many people find that the habits that once helped them maintain or even lose weight in their twenties or thirties simply don’t work the same way anymore. The truth is, your body has changed—and it’s not a failure of willpower or discipline.

Let’s unpack why.

 

1. Your Metabolism Naturally Slows Down

As you get older, your basal metabolic rate (BMR)—the amount of energy your body uses at rest—gradually decreases.

This happens for a few reasons:

  • Loss of lean muscle mass

  • Hormonal changes

  • Reduced energy demands from growth and development

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Even small changes matter. A slower metabolism means your body now needs fewer calories than it did before. So eating the same amount as you did years ago can quietly shift you into a calorie surplus.

 



2. You Likely Have Less Muscle Mass

Muscle is metabolically active—it burns more energy than fat, even at rest.

As we age (especially from our late 20s onward), we naturally lose muscle if we’re not actively maintaining it through resistance training.

Less muscle = lower calorie burn.

 

So even if your weight hasn’t changed dramatically, your body composition might have—leading to reduced energy expenditure.

 

3. Your Daily Movement Has Decreased

Think back to your younger years:

  • Walking between classes

  • Playing sports

  • Being generally more active without thinking about it

 

Now compare that to:

  • Desk jobs

  • Driving more

  • Structured (but shorter) exercise sessions

This reduction in non-exercise activity (NEAT) can significantly lower your total daily calorie burn—often without you realising it.

 

4. Hormones Play a Bigger Role

Hormonal shifts can affect:

  • Appetite

  • Fat storage

  • Energy levels

  • Insulin sensitivity

 

For women, changes related to menstrual cycles, contraception, pregnancy, or approaching perimenopause can all influence how the body responds to food.

For men, gradual declines in testosterone can affect muscle mass and fat distribution.

 

5. Recovery and Stress Matter More Now

When you were younger, your body could often “bounce back” quickly from:

  • Poor sleep

  • High stress

  • Irregular eating patterns


Now, these factors have a bigger impact:

  • Poor sleep can increase hunger hormones

  • Chronic stress can drive cravings and fat storage

  • Irregular eating can disrupt appetite regulation

 

So What Should You Do Instead?

See a dietitian! Let's help you figure out exactly what your body needs at your current age, weight, height and level of exercise. At Caylin Goodchild Dietitians, we’re here to help you achieve your weight loss goals in a way that's enjoyable, structured and delicious!


📍 Visit us in Lonehill at Concourse Medical Centre, or book a session online!





 
 
 

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