Intermittent Fasting is a method of voluntary fasting, usually for a certain number of hours a day with a specific goal to reduce body weight and change body shape or to achieve certain metabolic endpoints. Although it is quite a new fad the reason why it is gaining popularity is the thinking that for primitive man, food would have been scarce and that he would have had to go without food for prolonged periods of time. So Intermittent Fasting as apposed to frequent feasting (as we do in the 21st century) may actually have been the way we humans were biologically designed to eat. And that the habit of having three square meals and innumerable snacks in between is a modern one and probably the one that is causing an explosion of lifestyle diseases starting with the obesity and then progressing onto dyslipidaemia, hypertension, diabetes, cardiovascular disease and finally cancer. Further everything we do culturally and socially involves food and this therefore makes it very difficult for most of us to even consider Intermittent Fasting as a choice for better health (would you call it a party if food wasnt supplied by the host??). For a long time, I was a sceptic of intermittent fasting methods but the more I read and saw, the more I tended to believe in its benefits. Recently an uncle who at 85 yrs is a retired doctor and a national level athlete spoke about following a 18:6 IF regimen and triggered my interest in researching the medical evidence for IF. So here are some extracts and excerpts from what I have read.
What are the popular I.F regimens?
Daily time restricted feeding i.e., fasting for >12 hrs a day, alternate day fasting and 5:2 intermittent fasting (starving 2 days each week and eating normally on other days) are the. 3 most popular methods of IF.
So what happens in the body when you start Intermittent Fasting?
During I.F the energy producing mechanisms essentially change from being glucose based to one dependant on ketone bodies. All food that is digested is stored in the the liver as glycogen. Glycogen is essentially a long string of glucose molecules bound togetherin chains. In times of need, individual molecules of glucose are released for the use of the body. When one does intermitted fasting, the glycogen stores are already depleted and so the body starts to dissolve the fat stores by releasing triglycerides which are converted to Ketone bodies in the liver. Ketone bodies are a denser source of energy for a variety of cells especially for the brain. Ketone body production starts to rise only after 8-10 hours of fasting suggesting a minimum of 12 hrs of fasting for any real benefit from I.F. Switching to Ketone bodies to provide energy results in reduced respiratory exchange ratio i.e., reduce usage of O2 and therefore reduced production of Carbondioxide, representing a more efficient process for production and usage of energy.
While it is not clear if the benefits of IF are due to simply weight loss alone or because of metabolic switching, the many benefits of IF include improved glucose regulation, improved blood pressure and heart rate control, improved endurance training and loss of abdominal fat and body weight. Other benefits include increased life span, improved memory, balance and coordination (in Alzheimers and Parkinson syndrome), reduced blood pressure, lipids and reduced occurence of spontaneous cancers and slowed growth of certain other cancers.
So what are the cellular changes brought about by I.F?
Reduced Oxygen usage in ketone body metabolism results in reduced production of corrosive free radicals and therefore reduced oxident mediated cellular damage. Ketone bodies have an effect in suppressing inflammation and reducing cellular stress and improving specific tissue growth and plasticity. Ketone bodies are potent signaling molecules and regulate the expression of various proteins and molecules that are known to influence health and aging. (PGC-1gamma, Fibroblast factor 21, NAD, sirtuins, PARP1 and ADP ribosyl cyclase).
IF and Obesity and Diabetes:
Compared to women who only reduced their food intake by 25%,women who followed a 5:2 IF program had a greater increase in insulin sensitivity and reduction in waist circumference although both groups showed equal overall weight loss. In young men who fast fo 16hrs a day and hit the gym for weight training have fat loss along with preserved muscle mass. IF is as effective as standard diets for weight loss. In rat models, IF is associated with greater muscular endurance.
Weight loss with IF is associated with improved insulin sensitivity and improved diabetic retinopathy. Markers of inflammation have also been noted to reduce especially in patients with Rheumatoid arthritis.
IF and Cardiovascular disease:
IF brings about reductions in Blood pressure, reduces heart rate and increases heart rate variability. Lipid profile also improves with reductions in the levels of LDL, Triglyceride and increase in HDL values. Improved indicators of cardiac health were noted as early as 2-4 weeks of starting IF.
IF and neurological disease:
In experimental animal models of IF hadve shown delayed onset of Alzheimer’s disease and Parkinson’s disease. IF increased neuronal stress resistence by bolstering mitochondrial function and DNA repair. GABAminergic transmission is enhanced and this can prevent seizures activity. IF reduces autoimmune demyelination in mouse models of multiple sclerosis and after traumatic and ischaemic spinal cord injury and leads to improved functional outcomes. In humans, IF has shown to improve memory (verbal spatial and working memory).
IF and Cancer:
IF reduces the occurence of spontaneous cancers and also my other types of induced cancers in mouse models. Calorie restriction with IF impairs energy metabolism of cancer cells, reducing their growth and rendering them suseptible to chemotherapy. Several studies with Glioblastoma suggest that intermittent fasting can suppress tumour growth and extent survival.
Suggested regimens for daily time restricted feeding
Month 1 10 hr feeding period 5 days a week
Month 2 8 hr feeding period 5 days a week
Month 3 6 hr feedine period 5 days a week
Month 4 6 hr feeding peiiod 7 days a week
Suggested regimen for 5:2 Intermittent Fasting
Month 1 1000Kcal 1 day a week
Month 2 1000 Kcal 2 days a week
Month 3 750 Kcals 2 days a week
Month 4 500 Kcals 2 days a week