Intermittent fasting traps and how to avoid them

Lauded for its its weight-loss and health benefits, intermittent fasting continues to surge in popularity. HFG dietitian Jess Burvill explores the latest science, common pitfalls and practical tips for fasting success.

Eating by the clock

Intermittent fasting is a way of eating which alternates between periods of normal eating and periods of complete fasting or very limited eating.

Practised for thousands of years for religious, cultural or spiritual reasons, fasting started making mainstream headlines after featuring in the 2012 BBC documentary, Eat, Fast and Live Longer with Michael Mosley.

Unlike traditional diets which restrict energy (kilojoule/calorie intake), intermittent fasting focuses more on when you eat rather than what you eat.

The absence of kilojoule counting and ability to eat freely during non-fasting windows are two of the key reasons why intermittent fasting has become so popular.

Eat. Stop. Repeat.

Some popular intermittent fasting patterns include:

• 16:8 An eight-hour window of eating followed by 16 hours of fasting. 16:8 can involve skipping breakfast or dinner, and no nighttime snacking.
• 5:2 This method includes consuming only 2000-2500kJ (500-600 calories) on two non-consecutive days in a week, and unrestricted eating on the other five days.
• Alternate-day fasting Days of complete fasting are alternated with days of unrestricted eating.

Intermittent fasting mimics the eating patterns of our ancestors who often had periods of feast and famine

What does the science say?

Now that intermittent fasting has been around for a while, we have more research exploring the effects on health. Let’s unpack some of the latest findings.

Weight loss

Research shows intermittent fasting is effective for weight loss compared with regular eating. This makes sense because shortening your eating window results in lower overall food intake and fewer kilojoules consumed, which is crucial for weight loss. But is it more effective than other eating patterns? A recent large review of scientific evidence found no evidence that fasting led to more or longer-lasting weight loss than kilojoule-restricted diets. Some studies showed intermittent fasting could lead to more muscle loss than other diets, highlighting the importance of maintaining protein intake and strength-building exercise while fasting.

Diabetes and heart health

Many studies show intermittent fasting can improve a number of heart-health markers including LDL (bad) cholesterol, triglycerides and blood pressure. Fasting has also been shown to reduce insulin levels and improve insulin sensitivity. This makes it easier for the body to use glucose for energy, leading to more stable blood sugar levels, which is key to preventing and managing diabetes. What we still don’t fully understand is whether these results are related to the reduced kilojoule intake and resulting weight loss from fasting, or if the fasting pattern itself plays a role.

Anti-ageing

It has been suggested that fasting can help reduce inflammation and slow down ageing via a process known as autophagy. Literally meaning ’self eating’, autophagy is our body’s natural way of cleaning out damaged cells and toxins to make way for new, healthier cells. During fasting, autophagy ramps up to provide our body with an alternative source of energy. At this stage we don’t have a lot of human research into the mechanisms behind fasting and autophagy, so there is still much to learn.

Brain health

Scientists have only recently started investigating the connection between fasting and brain health. Animal studies have shown intermittent fasting can improve memory, and help remove betaamyloid proteins from the brain, preventing the formation of plaques linked to Alzheimer’s disease. New research also suggests fasting could positively impact anxiety and depression symptoms. Further studies are needed to confirm these effects, and whether they are enhanced by other lifestyle factors such as exercise and diet quality.

What is the best time of day to fast?

Some experts suggest syncing eating and fasting periods with your circadian rhythm – the body’s 24-hour internal clock that controls our sleepwake cycles – can optimise metabolism. For example, on a 16:8 fasting regime, this might involve eating all meals during daylight hours 7am- 3pm, aligning with peak times for hormones related to eating. This can potentially lead to more efficient digestion and metabolism, reducing the likelihood of food being stored as fat tissue. Ultimately, though, the best time for fasting is the one that fits with your schedule and allows for a healthy and sustainable routine.

Fasting traps

Being ravenous

Skipping meals can make you ravenous, and this can result in overeating or making unhealthy food choices once you break your fast.

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Plan ahead to ensure you include meals that are high in lean protein, healthy fats and fibre, as these will keep you feeling full for longer.

Ignoring diet quality

Regularly cutting out meals can result in nutritional deficiencies if subsequent meals and snacks are not carefully balanced.

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Prioritise eating a wide variety of nutrient-dense whole foods during your eating window, including those typically eaten during skipped meals.

Dehydration

Fasting raises the risk of dehydration because you’re not getting all of the fluid and electrolytes you’d normally get from food. This can cause headaches and leave you feeling tired and light-headed.

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Remember to keep your fluid intake up during fasting periods and consider taking an electrolyte supplement.

Excess caffeine

Most fasting patterns allow black tea or coffee alongside water during fasting windows, which can result in overconsumption of caffeine to stave off hunger pangs.

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To avoid impacting your sleep, limit coffee to no more than 400mg a day, which is equivalent to approximately two espressos, four instant coffees or eight cups of tea.

Under-fuelling for exercise

Performing high intensity or longer exercise in a fasted stage, and not refuelling for several hours afterwards, can lead to fatigue, muscle wasting and can compromise recovery.

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Time your harder exercise sessions so they fall within your eating window or on non-fasting days.

Overdoing it

Some people may be tempted to push the accepted limits and try fasting for extended periods beyond what is healthy for them, which could lead to detrimental side effects.

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Listen to your body. Remember, intermittent fasting is meant to be a sustainable and enjoyable.

Is fasting for you?

Intermittent fasting shows promise as an effective alternative to traditional diets, and can work well for some people who enjoy the simplicity and fl exibility it offers. Fasting is best avoided if you are pregnant or breastfeeding, a child, teenager, have an eating disorder or are in recovery from one, or are on diabetes medication. If you’re considering trying fasting, speak to an accredited practising dietitian, who can guide you on the best approach and nutrient intake to suit your individual needs and goals.

DAILY DIET CHECKLIST

✔ Lean protein to help keep hunger at bay and prevent muscle wasting

✔ Plenty of fresh fruit and vegetables for essential vitamins and minerals

✔ Some heart-healthy sources of fats such as olive oil, nuts and avocado

✔ Wholegrain breads and cereals for a healthy digestive system and to fuel exercise

✔ Dairy or calcium-fortified dairy alternatives for bone and dental health

✔ 8-10 cups of water to keep you well hydrated.