And here's why....
It's a Trigger: For most people, the number on the scale is an emotional trigger and can set the tone for the day. Seeing a "good" number can make you feel great and seeing a "bad" number can create feelings of anxiety and frustration. We judge ourselves based on that number and that can affect everything from the way we eat, the way we dress and even the way we interact with others.
Our weight is affected by many factors that are no in our control:
Fluid balance and hydration: Certain foods can cause water retention while others can have a diuretic effect. Exercising can cause small muscle tears which also causes water retention around the inflamed muscle.
Poop. Yes, how often and how much you poop will affect the number on the scale.
Hormones. Women's hormone levels fluctuate throughout the month which can cause all sorts of fluid shifts.
Muscle. The number on the scale does not dictate your muscle mass. As a result, the number may stay the same or even increase if building muscle.
It can have negative side effects: Focusing too much on the number can lead top obsessing over food and your body. This can increase "food noise" and result in negative body image, lower self-esteem, and disordered eating.
The scale does not measure your health. How much you weigh is just a number and does not provide the bigger picture of your behaviors and therefore your overall health. Study after study shows that body size does not equal health.
It's only one of many tools to demonstrate progress. Focus on non-scale victories. How do your clothes fit? Are you able to walk further without losing your breath? Are you thinking differently about food when in an emotional state?