Your guide to intermittent fasting

When you fast, your body uses stored energy between meals. Over time, intermittent fasting may help with weight loss if it helps you eat fewer calories overall.

Fasting itself doesn’t guarantee weight loss on its own. If you eat more calories than your body needs during your eating window, you may not lose weight.

It can work well for some people because it reduces snacking, late-night eating, or grazing throughout the day. Others may find it makes them too hungry, tired, or likely to overeat later.

There are several ways to do intermittent fasting. The right option depends on your routine, health, appetite, and lifestyle.

Intermittent fasting can help some people lose weight, but that doesn’t make it automatically better than other weight loss methods.

The main reason it may work is that it can reduce your overall calorie intake. For example, if you stop snacking in the evening or reduce the number of hours you eat each day, you may naturally eat less. However, intermittent fasting may not work if you:

• Eat very large portions during your eating window
• Snack heavily after fasting
• Rely on high-calorie convenience foods
• Drink sugary drinks or alcohol regularly
• Feel so hungry that you overeat later
• Find fasting stressful or difficult to stick to

Weight loss is usually more successful when your eating pattern feels comfortable. If fasting makes you feel miserable, tired, or out of control around food, another approach may suit you better.

Intermittent fasting may have some benefits, especially when it helps someone lose weight or improve their eating habits. Possible benefits can include:

• Reducing overall calorie intake
• Cutting down on late-night snacking
• Providing structure around meals
• Supporting weight loss for some people
• Improving some health markers, such as blood sugar, cholesterol, or blood pressure, particularly when weight loss occurs

It’s important not to overstate these benefits. Many improvements may come from weight loss itself, rather than fasting specifically. A balanced diet, regular activity, good sleep, and long-term habits are still just as important.

Intermittent fasting is about timing, but food quality plays a large part too. During your eating window, try to choose balanced meals that include protein, fibre, fruit and vegetables, wholegrains, and healthy fats.

Good options include eggs, fish, chicken, tofu, beans, lentils, vegetables, fruit, wholegrains, yoghurt, nuts, seeds, avocado, and olive oil. Try not to use your eating window as a reason to eat very large meals or rely mostly on ultra-processed foods. This may leave you feeling sluggish and can make weight loss more difficult.

Most fasting methods allow water during the fasting window. Some people also drink plain tea or black coffee. Try to avoid drinks that contain calories during the fasting window, such as sugary drinks, milky coffees, smoothies, or alcohol. If you feel dizzy, faint, shaky, or very weak, stop fasting and seek advice.

Intermittent fasting can be simple for some people, but challenging for others.

When you first start, you may feel hungry, tired, irritable, light-headed, experience headaches, or be less able to concentrate. These symptoms may improve as your body adjusts, but fasting is not right for everyone.

It can help to start gently. For example, you might begin with a shorter overnight fast rather than jumping straight into long fasting windows.

Some people feel fine exercising while fasting. Others may feel light-headed, tired, or weaker than usual. You may prefer to plan workouts during your eating window or after a meal, especially if you’re doing intense exercise. Drink enough fluids and avoid pushing through if you feel dizzy or unwell.

If you have diabetes*, speak to your doctor before trying intermittent fasting. Fasting can affect your blood sugar levels and may increase the risk of low blood sugar, especially if you take insulin or medicines that can cause hypos.

Don’t stop or change diabetes medicines without medical advice.

*If you aren't sure if you have diabetes (or are at risk of it), we offer Advanced Diabetes Testing in our pharmacies.

As stated, intermittent fasting is not suitable for everyone. Speak to a GP, pharmacist, or dietitian before trying intermittent fasting if you:

• Are pregnant or breastfeeding
• Are under 18
• Are underweight
• Have diabetes
• Take insulin or medicines that can cause low blood sugar
• Take medicines that need to be taken with food
• Have a history of eating disorders or disordered eating
• Have a history of fainting or low blood pressure
• Have a long-term health condition
• Are recovering from illness or surgery

You should also avoid fasting if it makes you feel out of control around food, leads to bingeing, or causes guilt or anxiety around eating.

Intermittent fasting can be flexible, but it can also affect your social life. Eating windows may not always fit around family meals, work lunches, celebrations, or eating out. Some people enjoy the structure, while others find it stressful.

It’s okay to adjust your routine when you need to. A healthy eating pattern should fit your life, not make everyday life harder.

• Intermittent fasting may suit you if you like structure, don’t mind skipping meals, and find that shorter eating windows help you manage your appetite.
• It may not suit you if fasting makes you feel unwell, affects your mood, triggers overeating, interferes with medication, or makes your relationship with food more difficult.

There is no single best way to lose weight. The best option is one that supports your health and feels comfortable long-term.