Methodology
Why Crash Diets Fail Long Term
Francesco Zen, founder of ZTraining · Last updated June 20, 2026
"Total waste of time. Hunger always wins, it's a survival instinct."
The predictable sequence
Carbs and calories drop too low
From here, time does the rest of the damage on its own.
Energy and mood drop first
The body's response to severe restriction shows up mentally before anything else.
Binge and frustration follow
The inevitable result of fighting a survival instinct rather than working with it.
Why this isn't a sustainable strategy
These are, honestly, barbaric procedures with no real logic or knowledge behind them. The sequence is predictable every time, which is exactly why crash diets keep failing the same way regardless of who's running them.
Related: Why most fat loss plans fail · Why you regained the weight
Francesco Zen is the founder of ZTraining and ZLIFE, with 18 years of coaching experience working with executives across the UK, US, and UAE. He built Mr Z, an AI coach trained on his methodology to bring the same approach to a wider audience.