For the past three years, our friends and colleagues have been shrinking all around us. You probably know someone who is 'on the pen': an estimated 1.6million people in the UK are now using them.
The health secretary claimed twice earlier this month that the high-fat, low-carb keto diet can "cure" mental illness.
The compounds have exploded in popularity, but big questions about safety and effectiveness are still unresolved.
Some results have been hidden because they may be inaccessible to you
Show inaccessible results