(This is about extreme fasting techniques such as water fasting, not more moderate intermittent fasting)

Fasting may work for weight loss, but at the expense of other goals. If your goal is only to lose weight as fast as possible, maybe it makes sense. But most people want to:

  • build muscle
  • minimize loose skin
  • not gain the weight back
  • put nutrients in their body
  • shift to better eating habits for the long term
  • not sacrifice too much of their social life
  • be able to continue with their responsibilities like work without being distracted or moody
  • not sacrifice their mental health

In which case, it's likely that a slower, more sustainable approach (e.g. eating 500 fewer calories per day than you're burning) is more appropriate.