During the winter, it can be easy to overindulge and put on weight. It’s something we all struggle with, but what better time of year is there to spend time with family and friends? Christmas and New Year’s are great times to celebrate. But what about after the holiday celebrations are over and you’re left feeling a little fuller than you’d like to?
With more evidence than ever linking obesity with ill health, staying in shape is definitely not just about looking and feeling great. Decades of studies have demonstrated in both animals and humans that being overweight could increase the chance of health risks, including diabetes, heart disease, dementia and tumours. While continuous calorie restriction has been a popular method for losing weight for many decades, a great deal of public interest has developed in recent years around the topic of fasting as a method of weight loss.
What is fasting?
Fasting is the practice of choosing not to eat for a given period of time. Simple enough.
In recent years, literally thousands of self-help books have been made available on the topic of fasting and there are a wide range of approaches and schools of thought on the topic.
Historically, fasting has used been as a therapeutic and religious practice in a wide range of traditions across the world for thousands of years. Even the ancient Greek philosopher Plato, who lived in the 5th century BCE, was said to fast for “mental and physical efficiency” (1). During this time, fasting was also recommended as a treatment for certain forms of illness, often considered to be an essential process of purification. So much so, in fact, that athletes preparing ahead of the Olympic Games were encouraged to fast.
In recent years, fasting has been recognised and popularised for benefits to general health, wellbeing and for supporting weight loss. At present, a number of randomised trials and experimental studies have shown that reduction in daily calorie intake by fasting can potentially delay the onset of disease and promote quality of life. (2,3)
Different types of fasting
There are a few different methodologies for fasting. The most researched methods are two types of intermittent fasting, including the “16:8 diet ” and the “5:2 diet”. (2)
For the ”16:8”, the aim is to abstain from eating for a 14-16 hour period, typically beginning in the morning; followed by an 8 hour eating window. Whereas in the “5:2” diet, eating is only restricted on any two days of the week, to a 1 or 2 small meals, typically around 300-600 calories each.
Regardless of the specific method, during the “eating window”, it’s really essential to eat lots of nutrient dense, healthy food. Filling the eating window with junk meals is likely to hinder progress, and could leave your body lacking in essential nutrients.
Other proposed methods include the “24 hours fast”, where a 24 hour cessation from eating is undertaken, often from dinner-to-dinner, skipping lunch and breakfast on a given day. “Alternate day fasting” proposes that one fasts every other day, consuming only around 300-600 calories on these days, and eating a normal balanced and full diet on every other day.
What are the benefits of fasting?
Regardless of the precise methods, during a fast, your body goes through a process of burning available reserves of energy. Firstly, the available glucose (sugar) in the body is utilised, next glycogen (stored glucose) is burned up, before finally the body starts to enter a state of ketosis (metabolising fat to fuel the body’s function).
In a state of ketosis, the body actively oxidises fatty acids from fat stores and turns them into ketones, supporting weight loss. Fasting can also support a reset in insulin sensitivity, decreasing the amount required by the body and is produced by the pancreas. (3)
Beyond weight loss, there is some evidence to suggest fasting is also beneficial for cardiovascular health2. During a fast, not only does the body consume ketones for energy, but LDL (bad) cholesterol is also used up. High levels of LDL cholesterol can be associated with strokes and heart attacks, so reducing them can have a positive impact on health outcomes.
Recent papers have suggested that fasting might help the brain in unexpected ways - supporting neuroplasticity and resistance to injury and disease. This makes sense from an evolutionary perspective, with our ancestors needing mental performance to find food sources at the time which they are most hungry.
While not conclusive, some limited animal studies have shown that fasting could possibly have a positive impact in augmenting the effectiveness of cancer treatments. Earlier studies have observed similar promise in human cancer patients. Fasting shows promise in protecting healthy cells, while not protecting cancerous cells from the toxicity of chemotherapy medicine.
When to avoid fasting
Intermittent fasting is typically safe and well tolerated by most people. However in some cases it should be avoided. Children, pregnant women, those with issues around hypoglycemia and anyone struggling with a serious and/or chronic disease should avoid fasting. Don’t hesitate to speak to a healthcare professional if you’re unsure if intermittent fasting is safe for you.
Many fasters report feeling the hungriest during the first few days of adjusting to their new fasting routine. We’d recommend consuming bone broth, or other very-low calorie drink which is rich in minerals if you’re really struggling during this time. If you’re feeling particularly unwell or uneasy - break your fast!
If you’re making the change from a high-sugar, high-carb diet, it can take longer to adapt to a fasting lifestyle and require more gradual steps. In some cases, feeling “woozy” can be a result of depleted electrolytes - in which case, we recommend consuming a supplement to replenish these in your body. What’s your experience with, and have you seen benefits from intermittent fasting? We’d love to hear from you in the comments below.
- Eat Fast Slim: The Life-Changing Fasting Diet for Amazing Weight Loss and Optimum Health: Amanda Hamilton
- An evidence based summary of the research into intermittent energy restriction / intermittent fasting for weight management in adults: BDA Obesity Specialist Group
- A time to fast, Andrea Di Francesco et al: Science Mag, November 16th 2018