Intermittent fasting (IF) is an eating pattern that focuses on when you eat, rather than what you eat. Instead of spreading meals across a 14-hour window, IF shortens the eating window to encourage longer fasting periods—typically 14–16 hours. This pushes the body to use up glucose and glycogen stores before switching to fat burning, a process known as metabolic switching or ketosis. The most common methods include the 16:8 plan (16 hours fasting, 8 hours eating) and the 5:2 diet (normal eating five days a week, with restricted calories on two non-consecutive days).
Research suggests IF can support weight loss, improve insulin sensitivity, trigger cellular repair processes such as autophagy, and even increase human growth hormone (HGH) levels. Some studies also indicate potential benefits for memory, brain health, and longevity. However, IF is not without drawbacks. Hunger, fatigue, and mood swings are common, while poorly managed fasting can lead to malnutrition, binge eating, or worsen eating disorders. Women may also face hormonal imbalances. Importantly, a large study found that people who restricted eating to less than 8 hours a day had a much higher risk of cardiovascular death compared to those with longer eating windows.
IF may be effective as a short-term weight loss tool, but it is not suitable for everyone. People with chronic conditions, children, teenagers, and those with a history of eating disorders should avoid it. Consulting a family doctor before starting is essential.
Intermittent fasting is a dietary schedule that creates an extended fasting window, typically within a 24-hour eating cycle. Unlike most fad diets, intermittent fasting does not focus on what you eat, but on when you eat.
An average, non-fasting adult might have breakfast at 8 am, lunch at 1 pm, an evening snack around 4 pm, dinner at 8 pm, and sometimes dessert or a late-night snack at 10 pm. This creates an eating window of roughly 14 hours (8 am to 10 pm), followed by a fasting window of about 10 hours while asleep.
Intermittent fasting increases the fasting window to about 14–16 hours (sometimes more), pushing the body to exhaust its glucose reserves before switching to burning stored fat. The primary goal is usually fat loss.
Often touted as a “modern metabolism hack”, intermittent fasting is popular among people seeking to lose weight when traditional diet and exercise strategies have not worked. But is it really the magical solution it is claimed to be? Let’s investigate.
When you fast for long periods, your body first uses the glucose in your blood and glycogen stored in your liver and muscles. Once these reserves are depleted, it begins burning fat for energy. This shift, called metabolic switching, is also known as ketosis.
Intermittent fasting is scientifically supported for fat burning and weight reduction. Beyond weight loss, fasting may provide additional health benefits:
While promising, IF does not work for everyone, and much supporting research is based on animal studies. Reported drawbacks include:
IF is not a universal solution. Medical guidance is essential before starting.
Suitable candidates: Healthy adults without chronic health issues who want to lose weight and can maintain balanced nutrition during fasting.
Not recommended for:
Evidence shows IF can be effective as a short-term strategy (3–6 months). Many people lose weight because the restricted eating window naturally reduces calorie intake.
However, problems arise when IF is practised long term:
The success of intermittent fasting depends heavily on individual health, lifestyle, and psychological factors. For some, it can be an effective short-term tool for weight loss and metabolic health. For others, it may be risky or unsustainable.
Always consult your family doctor before starting IF. It is unlikely to work as a stand-alone weight-loss solution and should ideally be combined with a balanced diet and regular physical activity.
Before adopting intermittent fasting, especially as a long-term strategy, it’s important to assess whether it suits your health and nutritional needs. Kauvery Hospital, with branches in Chennai, Hosur, Salem, Tirunelveli, and Trichy, offers expert medical guidance, metabolic evaluation, and personalized nutrition advice to help you choose safe, sustainable approaches to weight management.
Is long-term intermittent fasting safe?
Long-term intermittent fasting is not safe for everyone. While short-term fasting may support weight loss, prolonged fasting may increase the risk of nutrient deficiencies, hormonal imbalance, and heart complications. Medical supervision is strongly recommended.
What are the health risks of practicing intermittent fasting for years?
Possible risks include vitamin and mineral deficiencies, fatigue, menstrual irregularities, binge eating patterns, muscle loss, and increased cardiovascular risk, especially with very short eating windows.
Can intermittent fasting increase heart disease risk?
Some research suggests that restricting eating to less than 8 hours daily may be associated with a higher risk of cardiovascular death. More research is ongoing, but heart health should be monitored carefully.
Does intermittent fasting affect women differently?
Yes. Women may experience hormonal disruptions, irregular periods, hair loss, mood changes, and metabolic stress if fasting is too restrictive or prolonged.
Can intermittent fasting cause nutritional deficiencies?
Yes. If meals during the eating window are not balanced and nutrient-dense, long-term fasting can lead to deficiencies in protein, iron, vitamin B12, calcium, and other essential nutrients.
Is intermittent fasting good for long-term weight loss?
It can help with short-term weight loss. However, long-term success depends on overall diet quality, calorie balance, and lifestyle habits. Many people regain weight if sustainable habits are not developed.
Can intermittent fasting worsen eating disorders?
Yes. Intermittent fasting can trigger unhealthy food restriction cycles, binge eating, or worsen existing eating disorders. It is not recommended for individuals with a history of disordered eating.
Who should avoid intermittent fasting?
Children, teenagers, pregnant or breastfeeding women, people with diabetes, heart disease, low blood pressure, or eating disorders should avoid intermittent fasting unless closely supervised by a doctor.
Does intermittent fasting help reduce belly fat?
Intermittent fasting may reduce overall body fat, but it is not proven to be more effective than traditional calorie-controlled diets in specifically reducing visceral belly fat.
Should I consult a doctor before starting long-term intermittent fasting?
Yes. A medical consultation helps assess metabolic health, medication interactions, and potential risks before beginning or continuing intermittent fasting long term.
Kauvery Hospital is globally known for its multidisciplinary services at all its Centers of Excellence, and for its comprehensive, Avant-Grade technology, especially in diagnostics and remedial care in heart diseases, transplantation, vascular and neurosciences medicine. Located in the heart of Trichy (Tennur, Royal Road and Alexandria Road (Cantonment), Chennai (Alwarpet, Radial Road & Vadapalani), Hosur, Salem, Tirunelveli and Bengaluru, the hospital also renders adult and paediatric trauma care.
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