David Goding puts the chill diet under the microscope.

What is the 'chill diet'?
Forget relying on pernickety manipulations of what you put in your mouth – the latest left-field entrant to the weight loss realm adds freezing your butt off, a.k.a. cold therapy, to burn extra calories, of course.

Explored by Tim Ferriss in his wide-ranging The 4-Hour Body (which incidentally also covers: how to sleep two hours per day and feel fully rested; how to produce 15-minute female orgasms; and how to pay for a beach vacation with one hospital visit), cold could well be the secret behind why Everest explorers need to eat truckloads of lard in order to prevent catastrophic weight loss and why champion swimmer Michael Phelps can get away with eating 12,000 calories a day.

Ferriss says the practice is an easy – and reasonable – DIY endeavour.

"Place an ice pack on the back of the neck or upper trapezius area for 20 to 30 minutes, preferably in the evening, when insulin sensitivity is lowest.
"Consume at least 500 millilitres of ice water on an empty stomach immediately upon waking. (Or) Take five-to-10-minute cold showers before breakfast and/or before breakfast."

The science
Short-term cold exposure of around 30 minutes can lead to fatty acid release and provide fuel for heat production through shivering, leading not only to weight loss, but some lean muscle gain.

"Even at shorter durations, cold exposure with shivering could increase adiponectin levels and glucose uptake by muscle tissue," says Ferriss. "This effect could persist long after the cold exposure ends."

Cold also appears to stimulate thermogenesis of BAT fat (brown adipose tissue).

"BAT is sometimes referred to as 'fat-burning fat'," says Ferriss." Cold stimulates BAT to burn fat and glucose as heat. BAT helps dissipate excess calories as heat. These calories would otherwise be stored in WAT (white adipose tissue, or white fat) and end up in your beer gut or muffin top."

Conclusion

Granted, an extreme diet mightn't actually work, but that's the case with virtually every diet you're likely to come across.

NEXT: 5 hormones that cause weight gain>>