Weight loss surgery doesn't meet the 'strict' threshold required to withdraw KiwiSaver funds.

Three people have applied for the early release of their retirement savings on the grounds of serious illness, and all three applications were rejected.

Financial advisor Liz Koh says the threshold to withdraw KiwiSaver funds under 'serious illness' is very high, and applicants will need a condition that hinders their ability to work or poses a risk of death.

"You could also apply under the financial hardship rules, which means that you can actually be eligible to withdraw to pay for medical treatments for yourself, or if you have a serious illness. Of course, you have to demonstrate financial hardship."

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