Intermittent fasting, a diet strategy whereby calories are restricted by 75-90% [1] 1 to 2 days per week is not a new concept; however it has recently been gaining popularity, especially in the quest for weight loss.

Intermittent fasting and weight loss

In our current society with increasingly sedentary lifestyles, obesity is on the rise. Defined by the World Health Organisation (WHO) as a BMI greater than or equal to 30, it has almost doubled Worldwide since 1980.

As a method of weight loss, intermittent fasting has been well documented. An article published by Klempel [1] revealed that following a 24-week randomised clinical trial (on obese women) bodyweight reduction was documented at 7%, with LDL cholesterol decreasing 10% and triclyceride concentration by 17% through intermittent fasting.

Further research presented in the study had subjects face calorie restriction- either on a food based diet (IFCR-F) or replacing 1-2 meals with liquids (IFCR-L). After the 8-week study, results showed that combining intermittent fasting and caloric restriction is effective in reducing bodyweight, fat mass and visceral fat in obese women. Further, the results noted changes in coronary heart disease indicators namely: Decreased LDL Cholesterol and decreased triglycerides. Weight loss was reported in both the IFCR-L and IFCR-F diets with the food based group reporting a 2.6% weight loss with the liquid achieving greater loss at 4.1%

Metabolic changes

A study by Kerndt [2] conducted a 36 day fasting study on subjects fasting for religious beliefs. They noted that the following changes: Decreased blood (plasma) glucoses levels, increased lipolysis and ketogenesis. Lipolysis is the breakdown of fats to produce fatty acids whereas ketogenesis is where ketones are produced by the further breakdown for these fatty acids. Gluconeogenisis increased, which is the process where the body produces glucose from non- carbohydrate sources such as fatty-acids (glycerol). These metabolic changes are important, especially in the context of fat loss.

It should be noted, this study was conducted over 36 days, and therefore a longer study may be required to provide further evidence of these benefits


[1] M.C. Klempel,  C.M Kroeger,  S. Bhutani,  J. F. Trepanowski and K.A. Varady. “Intermittent fasting combined with calorie restriction is effective for weight loss and cardio-protection in obese women.”

[2] P.R. Kerndt , J.L. Naughton and C.E. Driscoll. “fasting: the history, pathophysiology and complications”

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