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. Traditionally religious practices often include intermittent fasting [2]. Ramadan, practiced by Muslims, involves fasting during daylight hours (during the 9th month of the Muslim calendar.)
Intermittent fasting would have been normal practice for our Palaeolithic ancestors. Here they would eat what they killed, but would first have to catch it. Many hunting hours would be fuelled by grazing on seeds, nuts, fruits- whatever foods were available growing wild. The paleo style of diet gave birth to ‘the warrior diet’, a system devised by Ori Hofmekler. [5]
Types of Intermittent Fasting
1) Warrior Diet
As mentioned previously, ‘the warrior diet’ is based on the habits of our Palaeolithic ancestors. Each day involves a period of “under eating” during the daily hours, until the “over eating” phase in the evening. The under eating phase involves eating small portions of raw fruit, vegetables, nuts and light protein. The aim is to:
- Detoxify and cleanse the body
- Maximise hormone efficiency
- Burn fat
The overeating phase of this type of intermittent fasting is to:
- Boost metabolism
- Replenish energy
- Enhance recovery of tissues
Having under eaten during the day, the body is now adjusted to consume the majority of your daily calories, without gaining fat.
2) 5:2 Diet strategy
The 5:2 intermittent fasting strategy involves eating ‘normal’ calorie requirements for 5 days per week and severely restricting consumption on 2 days. Research published in the “British Journal of Diabetes and Vascular Disease” states that for fasting days, calorie consumption for men should be <600 calories per day and <500 for women.
The study by J.E. Brown et al. (2) highlights that this method of intermittent fasting “has been shown to be similarly effective or more effective than continuous modest calorie restriction with regard to weight loss and improved insulin sensitivity”
Intermittent Fasting & Calorie Restriction.
Research on intermittent fasting published by Klempel et al. [1] reports a study of fasting for 1-2 days per week (with a calorie restriction of 75-90%) for a 24-week randomised trial on obese women. Results showed a 7% reduction in bodyweight, 10% reduction in LDL cholesterol (the bad one) and 17% reduction in Triglyceride concentrates. 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. The food based group reported 2.6% weight loss with the liquid achieving greater loss at 4.1%
References
[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] J.E. Brown, M. Mosley and S. Aldred. “Intermittent fasting: a dietary intervention for prevention of diabetes and cardiovascular disease?”
[3] F. R. de Azevedo, D. Ikeoka and B. Caramelli. “effects of intermittent fasting on metabolism in men”
[4] M. P. Mattson and R. Wan. “Beneficial effects of intermittent fasting and caloric restriction on the cardiovascular and cerebrovascular systems”
[5] O. Hofmekler., 2007 “The Warrior diet”. 2nd edition, Blue snake books, Berkeley.
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