To fast or not to fast

There is a growing body of evidence suggesting that periods of fasting can offer significant benefits for our physical health. Understandably, many of us are intrigued by fasting, especially since the 5:2 diet gained popularity about ten to 15 years ago through the late Dr Michael Mosley’s work. This method, which involves eating no more than 500 to 600 calories on two non-consecutive days each week while enjoying normal meals on the other days, has helped many individuals achieve their weight-loss goals – as long as they avoid overindulging on non-fasting days to make up for any calorie deficit.

Intermittent fasting has continued to make waves, with various approaches emerging as popular strategies. While the terms ‘intermittent fasting’ and ‘time-restricted eating’ are often used interchangeably, it’s important to grasp the nuances that differentiate them. Time-restricted eating usually involves a consistent daily eating schedule, whereas intermittent fasting may include longer fasting periods at irregular intervals. Regardless of the method, the goal remains the same: to refrain from consuming calories during specific times. During a fast, you are allowed to have water, black tea and coffee; however, milky drinks and food must be set aside.

Common practices include the 12:12 method, where you fast for twelve hours and eat during the remaining twelve hours, and the 16:8 method, which consists of 16 hours of fasting followed by an eight-hour eating window. Some may even choose to fast for longer periods. It’s essential, however, to focus on nourishing your body during non-fasting times and resist the temptation to indulge in unhealthy or poorly nutritious foods.

Helpful or harmful?

As with many diets or eating patterns, there is mixed advice about whether intermittent fasting is beneficial or harmful. Much of the current research has focused on animal studies, revealing promising improvements in metabolic and cardiovascular health. While human studies are gradually emerging, we still lack comprehensive long-term data on the risks and benefits, as fully understanding these effects often takes decades. 

Let’s take a moment to acknowledge some of the concerns surrounding fasting. Short-term effects can include headaches, lightheadedness, mood swings, fatigue and difficulty concentrating – feelings that many of us can relate to when we experience ‘hanger’. Critics argue that fasting may put excessive stress on the body, leading to increased cortisol levels and, while research is ongoing, we have yet to determine whether this results in long-term harm.

There is also a valid concern that fasting could promote disordered eating or binge behaviour. It’s crucial to be mindful of the quality of food you consume during your eating windows, as a lack of focus on nutrition can lead to malnutrition and muscle loss.

On the other hand, there are many compelling arguments in favour of fasting and time-restricted eating. One of the most appealing aspects is its simplicity. Tracking an eating schedule can be as easy as watching the clock. For instance, if you follow a 12:12 regimen, you start eating at 8am and stop at 8pm, maintaining this routine consistently day after day. This approach can effectively help eliminate late-night snacking after dinner.

Emerging evidence suggests that intermittent fasting can support weight loss, likely due to calorie restriction, though the exact mechanisms are still being explored. Additionally, studies indicate that it may improve blood glucose control, reduce the risk of type 2 diabetes, lower cholesterol levels, decrease blood pressure and potentially alleviate the risk of heart disease.

Another important consideration is how intermittent fasting affects the gut microbiome, which is a complex community of bacteria that plays a crucial role in our overall health. Allowing periods without food can create an environment that helps beneficial gut bacteria thrive. You can think of these helpful bacteria as a ‘cleaning crew’ that works diligently to keep our systems in balance when no food is present, similar to office cleaners efficiently tidying up an empty office.

However, it’s essential to recognise that intermittent fasting may not be suitable for everyone. Certain groups should be cautious, including:

• pregnant or breastfeeding women
• individuals with a history of eating disorders
• those with type 1 diabetes
• people on medication that must be taken with food
• older adults.

If you’re unsure whether intermittent fasting is the right choice for you, I encourage you to reach out to your healthcare provider for guidance tailored to your individual needs. 

Fasting as a spiritual practice

Finally, let’s take a moment to consider the spiritual aspect of fasting, as it offers so much more than just its physical effects. Throughout the Bible, we see fasting mentioned in both the Old and New Testaments, and it was embraced for a variety of reasons. People fasted to strengthen their prayers, seek God’s guidance, express their grief, find deliverance or protection and to show repentance. For example, in 2 Samuel 12:16-23, David fasted and prayed to God for the healing of a child, Ezra fasted for protection and guidance on the journey to Jerusalem (Ezra 8:21-23). In the New Testament, we see the early Church use fasting and prayer to commit the newly appointed elders to the church (Acts 14:23).

For many Christians, choosing to fast is a deeply personal and spiritual journey. While Jesus never explicitly states that fasting is a requirement, he instructs his disciples in Matthew 6:16: “When you fast.” This could suggest that fasting is expected, but it likely reflects the cultural context of the time, where fasting was an important part of Jewish customs. Today, this practice can serve as a profound way to connect with faith and purpose.

Benefits and methods of intermittent fasting

Intermittent fasting offers potential health benefits such as weight loss, improved blood glucose control and reduced risk of heart disease.

Common methods include the 12:12 (twelve hours fasting, twelve hours eating) and 16:8 (16 hours fasting, eight hours eating) routines.

Maintaining a nourishing diet during eating windows is crucial to avoid nutrient deficiencies.

Risks and considerations

Short-term side effects can include headaches, fatigue and mood swings.

Certain individuals should avoid fasting, such as pregnant or breastfeeding women, those with a history of eating disorders and people with specific medical conditions.

Consulting a healthcare provider is recommended before starting fasting.

Spiritual benefits

Beyond physical benefits, fasting has a strong spiritual tradition, particularly in Christianity.

People have historically fasted for guidance, repentance and deepening their faith.

As John Piper stated: “Fasting is a way of saying with our stomach and whole body how much we need, want, and trust Jesus.”