Intermittent Fasting May Help Weight Loss, Experts Say

ISLAMABAD (News Desk) – Intermittent fasting has gained widespread popularity as a strategy for weight management and better health, but nutrition researchers say some of the more ambitious claims surrounding the eating pattern are not yet supported by strong human evidence.

Studies indicate that intermittent fasting can help people lose weight and may improve certain measures of metabolic health, including blood pressure and cholesterol. However, research so far has not established that fasting is significantly more effective than other proven dietary approaches.

What is intermittent fasting?

Intermittent fasting refers to an eating pattern in which food is consumed during designated periods while intake is restricted during the remaining hours or days.

One popular approach is the 16:8 method, in which people fast for 16 hours and eat within an eight-hour window. Other strategies involve significantly reducing calorie intake on particular days of the week.

The approach is commonly used for weight management, although researchers are also investigating its potential effects on metabolic health.

Experts stress that intermittent fasting should not be equated with Ramadan fasting. Ramadan is a religious practice in which Muslims abstain from food and drink from dawn until sunset throughout the holy month, with the practice centred on worship, discipline and empathy rather than primarily on weight loss.

What does the evidence show?

Intermittent fasting is often promoted as a way to improve metabolism, regulate blood sugar, lower blood pressure, encourage cellular repair and potentially reduce the risk of serious diseases.

Researchers, however, say evidence for many of these broader health claims remains limited.

Krista Varady, a nutrition researcher at the University of Illinois Chicago, has said intermittent fasting should not be viewed as a “magic” solution.

Research does show that fasting can contribute to weight loss, Varady has noted, but it has not been shown to consistently outperform other effective approaches to dieting.

Animal research produced striking results

Some of the earliest research into fasting involved animals, including mice, flies and worms.

When food is unavailable, the body can shift from relying primarily on glucose to using stored fat for energy. Fasting may also trigger autophagy, a cellular process through which damaged or ageing components are broken down and recycled.

Animal research has associated these mechanisms with various potential health benefits, including longer lifespans.

In some experiments, mice consuming similar amounts of calories remained leaner and appeared healthier when their food was restricted to specific periods.

Scientists caution, however, that findings from animal experiments cannot automatically be applied to humans.

Weight loss generally around 5%

According to Varady, various forms of intermittent fasting typically produce weight loss of around 5% of body weight in human studies.

That reduction, however, is broadly similar to results seen with other successful dietary strategies.

Even relatively modest weight loss can have health benefits. Research has associated intermittent fasting with improvements in certain metabolic risk factors, including blood pressure and cholesterol.

Some studies have also reported possible improvements in symptoms linked to polycystic ovary syndrome (PCOS), particularly among people who begin with poorer metabolic health.

Researchers caution that more aggressive approaches, including alternate-day fasting, could increase the risk of losing lean body mass and muscle.

Cancer and brain-health claims remain unproven

Fasting has also attracted attention because of claims that it could protect brain health or lower cancer risk.

Scientists say, however, that there is still a considerable gap between promising laboratory findings and evidence from human clinical trials.

Animal experiments have suggested that fasting could potentially influence cancer-related processes and might protect healthy cells during chemotherapy. Such effects have not been conclusively demonstrated in humans.

One study involving a 5:2 fasting approach reported possible benefits for some women with metastatic breast cancer undergoing chemotherapy, including improvements in quality of life and disease progression.

Researchers emphasise that such findings remain preliminary and should not be interpreted as a general recommendation for cancer patients.

What people eat remains difficult to measure

A major challenge in intermittent-fasting research is determining exactly what participants eat.

Researchers can precisely control food intake in animal studies, but monitoring people’s diets in everyday life is considerably more difficult.

Participants are frequently asked to keep food diaries, but people may forget meals, leave out snacks or underestimate portion sizes.

Varady has said that only about half of participants in her research return complete dietary records.

A 2025 estimate by an international research team suggested that people may underestimate their actual food consumption by roughly 400 to 800 calories or more, further complicating nutrition research.

Technology could improve future studies

Scientists are investigating technologies that could provide more accurate information about eating habits without relying entirely on self-reported food diaries.

Some research uses photographs of meals, while other projects are testing cameras integrated into glasses or devices worn around the neck to record eating and chewing.

Such approaches, however, raise obvious privacy concerns.

Researchers are therefore also exploring non-camera alternatives, including neck-worn devices that detect chewing, smart forks that monitor eating movements and sensors placed on teeth to identify dietary components.

Most of these technologies remain experimental.

Blood and urine tests may offer better insights

Biological testing could provide another way to measure dietary intake more accurately.

Blood and urine analyses may help researchers determine which nutrients people have consumed and how their bodies respond to them.

Thomas Wilson, a nutrition researcher at Aberystwyth University, has suggested that future studies could combine food diaries with blood and urine biomarkers and information collected through wearable devices.

Such methods could give scientists a more complete picture of dietary habits while allowing participants to maintain their normal routines instead of following highly controlled diets.

Does intermittent fasting actually work?

The evidence so far suggests that intermittent fasting can support weight loss and may improve some measures of metabolic health, but there is not enough evidence to describe it as a uniquely powerful or “magic” diet.

Researchers also warn against drawing direct conclusions from animal studies when assessing its effects on humans.

Diet quality, exercise, sleep and other lifestyle factors can influence health outcomes, making it difficult to determine how much benefit comes specifically from fasting.

For people considering intermittent fasting, the broader evidence suggests that what and how much a person eats may matter at least as much as when they eat.