An introduction to Intermittent Fasting
In my practice, I have found this to be the most successful strategy for achieving weight loss.
The paradigm regarding weight loss for the last forty years to ‘eat less, move more’ or ‘calories in versus calories out’ could just have been wrong. The proof of which is in the pudding... populations are getting fatter. There is now a convincing amount of evidence to support the view that the timing of when we eat is important.
When we eat we are usually giving our body’s energy or fuel, at anyone meal, more than we need for our immediate energy requirements — so this fuel needs to be stored for future use. The key hormone involved in both the storage and use of energy is insulin. Carbohydrates (and protein to a lesser extent) will stimulate the production of insulin. Fats barely have any effect on the insulin response. Insulin facilitates the transfer of glucose (the fuel) from the blood vessels, following the digestive process, to the cells where it can be used for energy or stored as fat for later use.
Energy is stored as glycogen in the liver and muscles for immediate use. Once the limit is reached, approximately 2000 calories or 24 hours fuel, the excess glucose is turned into fat. This newly created fat can be stored in the liver or in fat deposits in the body. The body cannot store protein, thus it is either used for repair and rejuvenation or it is converted into glucose. Dietary fat is absorbed straight into the blood stream following its journey through the digestive tract without passing through the liver.
When we don’t eat (fasting), insulin levels drop, which signal that we need to start burning stored energy. The easily accessible glycogen is used first. Once that is depleted, our bodies need to use our stored fat. Even if you have some glycogen stores left, if it is low enough and your insulin is low your body will have access to its fat store. However, for some people, whose diets constantly raise their insulin levels, the process may take longer to be initiated as they need to get their insulin levels lowered. They may have insulin resistance. ( I will write separately about this important topic.) The process, whereby the liver manufactures new glucose from stored fat, is called gluconeogenesis. After sometime fasting (it will vary from person to person), our bodies will start the process of lipolysis, a further pathway using stored triglycerides (fat) as the fuel source. These fatty acids can be converted by the liver to provide ketones which the brain can use as alternative fuel to glucose. Protein is thus preserved, unless there is no other fuel.
Four or five days after fasting is commenced, we start producing high levels of growth hormones which will help maintain muscle mass and lean tissue. Increased norepinephrine (adrenaline) levels will help prevent any decrease in metabolic rate. Insulin goes down and in time insulin sensitivity is improved (your cells become more responsive to normal levels of insulin to do its job). This lowering of insulin will cause excess salt and water to be excreted. In studies, electrolytes in the body (sodium, chloride, potassium, calcium, phosphorus and magnesium) remained stable. However, if you usually have a low salt diet a pinch of salt may be a useful supplement, and, as so many people are depleted in magnesium, ensuring adequate magnesium could be beneficial.
Types of Intermittent Fasting
People may choose to fast for a number of therapeutic reasons: treating type 2 diabetes, fatty liver disease, or other metabolic disorders. However, as my focus is to support people to lose weight, I will concentrate on fasting programmes best suited to weight loss. They will have the benefits previously listed but not necessarily as intensely.
The 5:2 diet
With this method you eat healthily for five days a week and for two you reduce your calories to 600 for a man and 500 for a woman.
This regime was famously popularised by Dr Michael Mosley in a BBC programme.
Short fasts 12 hours
This is basically what we used to do, before eating for up to 16 hours a day became the new normal! The idea is to finish your last meal at, say 19.00 hours and then not eat until 07.00 hours the next morning. Not really difficult!
16 hour fast
Finish eating at 19.00 hours and don’t eat again until 11.00. Again, not really hard! This means you have an eight hour window in which to eat either your three meals or just two meals.
20 hour fast
You get the picture! Fasting for longer does increase the health benefits, but it is best to find a system that works for you and that you can sustain. You can mix and match. You don’t have to fast every day. Fasting for weight loss is more powerful if combined with eating a healthy wholefood diet, and moving! Being in sync with your circadian rhythm also boosts the effects of fasting and, as part of this schedule, finish your last meal of the day at least three hours before you go to bed. (I have written an article on the circadian rhythm.) It is, of course, important to not over-compensate after your fast by eating too heartily.
Advantages of fasting
• Weight loss obvs!
• Improves mental clarity and concentration
• Lowers blood sugar
• Improves insulin sensitivity
• Increases energy
• Improves fat burning
• Lowers blood cholesterol
• May help prevent Alzheimer’s
• Extends life (and living)
• Reverses the ageing process
• Decreases inflammation
• It is simple
• It is free
• It is convenient
• You can enjoy life’s pleasures (in moderation)
• It is powerful (it works)
• It is flexible — it can be done anywhere. If you don’t feel well, stop. If you are on holiday, etc, just stop and start again!
• It works with any diet....vegetarian, gluten free, etc.
Side effects of IF
Hunger – hunger is frequently inspired by habit. When you first skip a meal, you may feel hungry. Mostly this passes, and if you are busy you won’t think about it again until your next meal is due!
Weakness and fatigue – this is unusual and mostly temporary whilst your body is learning, maybe for the first time in years, to burn its fat as fuel.
Who should not fast
• Anyone malnourished or underweight
• Children or young people under 18
• Pregnant and breast-feeding women
• Anyone with an eating disorder
Seek medical advice before commencing fasting if
• You are taking medications
• You have gout
• You have type 1 or 2 diabetes
• You have gastroesophageal reflux disease
Obviously this article is a quick romp through Intermittent Fasting, just giving highlights. Although very simple to do (‘just don’t eat’), if you are interested in IF, it is worth while finding support.