Intermittent fasting has become increasingly popular, but what does the science actually say about its effects on health and wellbeing?
Once primarily a religious practice, fasting has entered mainstream nutrition as a structured eating pattern. You’ve likely heard of the 5:2 approach, and perhaps variations like 16:8 or 18:6 — each referring to different time-based fasting schedules.
While restrictive diets can be difficult to sustain, intermittent fasting focuses less on what you eat and more on when you eat. For some people, this approach can fit well into daily life. Advocates suggest it may help with weight management, metabolic health, and even longevity. So what does current research tell us?
Not what, but when
Intermittent fasting is an eating pattern that alternates between periods of eating and fasting. Rather than limiting specific food groups, it sets time windows for eating. Research in the past decade has focused on these shorter, regular fasting periods rather than prolonged fasting over several days.
What the science shows
Early studies suggest that intermittent fasting may provide health benefits, including improved blood sugar control, better heart health markers, and reduced inflammation. However, results can vary between individuals, and more long-term research is still needed.
Fasting and weight management
Intermittent fasting often leads to an overall reduction in calorie intake, which can support weight loss. Some studies suggest it may help reduce visceral (abdominal) fat while preserving lean muscle mass — a key factor in maintaining long-term metabolic health. Comparisons between intermittent fasting and traditional calorie-controlled diets show similar or, in some cases, slightly better results with intermittent fasting for some individuals.
It can also help people become more comfortable with the natural feeling of hunger, reducing anxiety around eating and improving mindful eating habits.
Fasting and blood sugar regulation
Emerging research indicates intermittent fasting may improve blood glucose and insulin sensitivity, particularly in individuals with pre-diabetes or insulin resistance. Some studies report reductions in insulin levels of up to 20–40% after consistent fasting routines, which can contribute to better metabolic control.
Fasting and gut health
Preliminary studies, including human trials, suggest intermittent fasting may help reduce inflammation-related gut bacteria and increase bacterial diversity — both markers of good gut health. Allowing the digestive system to rest overnight for 10–12 hours can also support healthy circadian rhythms, which play a role in digestion and immune balance.
Fasting and brain health
Some studies suggest fasting may benefit brain function and memory. It may promote the growth of new neurons and strengthen connections between brain cells, which are thought to help protect against neurodegenerative diseases such as Alzheimer’s and Parkinson’s.
Fasting and heart health
Intermittent fasting may help lower blood pressure and reduce LDL (“bad”) cholesterol and triglyceride levels, potentially supporting cardiovascular health. Some research has shown decreases in triglycerides by up to 25% and modest improvements in blood pressure after several months of consistent practice.
Is it suitable for everyone?
Intermittent fasting may not be appropriate for everyone. It is not recommended for pregnant or breastfeeding women, children, individuals with high energy needs, or people with certain medical conditions. Always seek guidance from a doctor or registered dietitian before starting any fasting plan. Prolonged fasting can sometimes lead to fatigue, low energy, headaches, or muscle loss if not managed properly.
Example of intermittent fasting plans
| 5:2 Plan (Full-day fasting) | |
| Breakfast | Small coffee or tea |
| Lunch | Wholegrain crackers with tuna and tomato |
| Afternoon tea | Tea with milk or herbal tea |
| Dinner | Grilled chicken with mixed steamed vegetables |
| 16:8 Plan (Part-day fasting) | |
| Morning | Water, black coffee, or green tea until midday |
| Lunch | Wholegrain sandwich with avocado, salad, and lean protein such as salmon |
| Afternoon | Fruit and a handful of nuts |
| Dinner | Wholemeal pasta with vegetable-based sauce and side salad |
| Evening | Plain yoghurt with fruit; fast begins at 8 p.m. |
Tips for successful intermittent fasting
- Be realistic: Choose fasting days that fit your schedule and social life.
- Find consistency: Keeping a regular fasting pattern can help your body adapt.
- Stay hydrated: Aim for 8–10 glasses of water per day.
- Include protein: Add foods such as eggs, beans, and lentils to help maintain muscle and keep you full.
- Recognise hunger cues: Pause before eating to check if you’re truly hungry or just eating out of habit.
- Limit caffeine: Use coffee and tea in moderation, not as your main source of energy.
- Eat mindfully: Avoid overeating on non-fasting days; balance is key for sustainable results.
Understanding your fasting options
Intermittent fasting involves alternating periods of reduced or no calorie intake with periods of normal eating. Two common approaches include:
- Full-day fasting (5:2 approach): Reduced calorie intake (around 2000–2500 kJ) for one or two non-consecutive days per week, with normal eating on other days.
- Time-restricted fasting (16:8 or 18:6): Eating within a 6–8-hour window and fasting for the remaining hours of the day.
Fasting for 10–12 hours overnight has also been associated with improved digestion and gut balance. However, fasting is not a one-size-fits-all approach, and outcomes depend on individual health, diet quality, and lifestyle.
Risks and Recovery
Intermittent fasting can offer health benefits, but it may also cause temporary fatigue, irritability, or dehydration if not approached carefully. People with underlying health conditions or on medication should seek professional advice before starting. Always focus on balanced nutrition, hydration, and gradual changes to maintain safe and sustainable progress.
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