If you’re like many health-conscious women weighing themselves regularly, you’ve probably noticed that on some days the number on the scale seems to jump for no apparent reason. One day, your weight is down, and the next, it’s right back up again. It’s frustrating, isn't it? But here’s the thing: these fluctuations often don’t reflect your real fat loss progress. This is why a single reading on your scales can't be trusted.
Why Does Weight Fluctuate?
Body weight can change throughout the day, week or menstrual cycles due to several factors that have nothing to do with fat gain or loss. Here are the main causes:
1. Diet
Water retention from high salt intake: Salty foods cause your body to hold onto extra water.
Carbohydrate intake: Each gram of stored glycogen (carbohydrate) binds to 3 - 4 grams of water. So, after a carb-heavy meal, your weight may spike temporarily as your muscles store extra water. This also explains why you might feel more boated or 'puffy' after certain meals.
2. Sleep
Poor sleep quality: Inadequate sleep raises cortisol levels, which can lead to water retention and weight gain, even without changes in your diet.
3. Inflammation
Illness, injury, or stress: Inflammation causes your body to retain water as part of the healing process, which can result in temporary weight increases.
4. Supplements & Medications
Creatine: This popular supplement causes your muscles to hold onto water as part of its function in supporting muscle performance.
Medications: Some medications, such as anti-inflammatories, corticosteroids, and certain blood pressure drugs, may lead to water retention as a side effect.
5. Hormonal Shifts
Hormonal changes: Hormonal fluctuatios in the luteal phase of your menstrual cycle can lead to water retention. The combined oral contraceptive and thyroid imbalances may also affect weight.
6. Digestive Changes
Bloating, constipation, or digestion issues: Constipation or bloating from high-fibre foods or certain sensitivities can add temporary weight without reflecting changes in fat mass.
What’s a Normal Amount of Weight Fluctuation?
It’s important to remember that weight fluctuates naturally throughout the day, week and menstrual cycle. A normal weight fluctuation can be anywhere from 0.5 to 2 kilograms (500–2000 grams) in a single day, mostly due to changes in water weight, digestion, or hormonal shifts. This fluctuation is completely normal and doesn’t indicate actual fat gain or loss.
Why Waist Circumference is a Better Measure of Health
When it comes to monitoring weight loss and overall metabolic health, waist circumference is a much more reliable indicator than the number on the scale. Here’s why I, as a nutritionist, recommend waist measurement over weight:
1. It tracks fat loss, not water weight.
Unlike your overall body weight, which can change based on fluid shifts or muscle gain, your waist circumference directly reflects changes in abdominal fat. Research consistently shows that excess fat around the middle is a risk factor for metabolic syndrome (insulin resistance, high triglycerides, high blood pressure and low HDL) and eventual risk of type 2 diabetes and cardiovascular disease.
2. It focuses on disease risk prevention and longevity rather than aesthetics.
Waist circumference is a key marker of visceral fat, the type of fat that wraps around your internal organs and has the greatest impact on your health. Studies show that carrying extra weight around your waist increases your risk for metabolic syndrome regardless of your overall weight.
3.More motivation, less frustration.
Watching the scale yo-yo can be discouraging, especially if you’re working hard and not seeing immediate results. Waist measurement, however, gives you a clearer picture of fat loss and progress over time, which can be more motivating.
4.Backed by Science
Multiple studies highlight waist circumference as a better predictor of health risks than body weight or BMI alone.
How to Measure Your Waist
To measure your waist circumference, use a flexible tape measure. Place it around the narrowest part of your waist, just above your belly button (if you can't find your waist, measure at the point of the belly button). Keep the tape snug but not tight, and take the measurement at the end of a normal exhale.
Always test in the morning, before eating and getting dressed and make sure the same person carries out the measurement each time.
For women, a waist measurement of less than 80 centimetres is considered within a healthy range, while anything above could signal a higher risk for metabolic health issues and above 88cm a significant risk.
How to Use the Scales, if That's Your Preference
For the most accurate and consistent scale readings, it’s best to weigh yourself under the same conditions each time. Aim to weigh yourself either weekly or daily, ideally in the morning after using the bathroom and without clothes on. Be sure to use the same set of scales each time to reduce the variables. Rather than focusing on a single reading, look at your weight as a trend over time, because as you now know, daily fluctuations are normal. Observing trends rather than individual numbers can give you a clearer picture of your progress.
You can choose to track both measures, but by shifting your focus from the scale to waist circumference, you'll gain a clearer picture of your health progress and feel less discouraged by those daily weight fluctuations. Waist circumference is not just a number - it’s a tool that reflects real changes in your body composition, particularly around the belly, which is where it matters most for long term health and disease risk management.
If you're ready to address excess weight and unlock your weight loss potential, I’m here to help! I invite you to learn more about the Mind Body Makeover.
References
Ross, R., Neeland, I.J., Yamashita, S. et al. Waist circumference as a vital sign in clinical practice: a Consensus Statement from the IAS and ICCR Working Group on Visceral Obesity. Nat Rev Endocrinol 16, 177–189 (2020). DOI: https://doi.org/10.1038/s41574-019-0310-7
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