Why your weight goes up and down every day

You ate well all week, stepped on the scale and it went up. It's one of the most frustrating moments in any health journey, and one of the most common reasons people give up. Usually, nothing is wrong. Day-to-day weight changes are mostly about water, not fat.

What moves the scale

• Salt: a salty meal makes your body hold on to extra water for a day or two
• Carbohydrates: your body stores carbs as glycogen, and each gram is stored with roughly three grams of water
• Food in transit: the weight of food and drink that hasn't been digested yet
• Hormones: many people retain water at certain points in their menstrual cycle
• Exercise: a hard workout can cause temporary water retention as muscles recover
• Sleep, stress and timing: when you weigh yourself and what you've had to drink

Together, these can easily shift your weight by a kilo or more from one day to the next, which is far more than any real change in body fat.

How to weigh yourself

• Weigh at the same time each day, ideally first thing in the morning after using the bathroom
• Use the same scale on a hard, flat floor
• Weigh in similar clothing, or none

Watch the trend, not the day

A single weigh-in tells you very little. Weigh yourself a few times a week and compare weekly averages instead. If the average is moving in the right direction over two to four weeks, you're on track, whatever the scale said on Tuesday.

The scale isn't the only measure

How your clothes fit, your energy, your strength in the gym and how you feel day to day are all signs of progress too. Combining these with what you eat gives you the full picture. Mealful keeps your daily calories and macros in one place, so when your weight trend changes, you can see what your eating looked like at the time.