Can intermittent fasting aid in weight loss?

Intermittent fasting — a weight-loss method based on timed eating schedules — is gaining popularity. But how effective is it?

Dr Frank Hu, a professor of nutrition and epidemiology at the Harvard TH Chan School of Public Health, states that "intermittent fasting has a similar or even modest benefit over traditional calorie-restriction dieting for weight loss."

The simplicity of intermittent fasting might make it more appealing and easier to maintain than other weight-loss plans, according to a report reviewed by Dr Howard E LeWine, chief medical editor at Harvard Health Publishing. 

The focus on when, not what

Unlike many diets regulating what and how much to eat, intermittent fasting centres around when you eat. 

One of the most common methods is the 16/8 schedule, where individuals limit their eating to an eight-hour window, such as from 10am to 6pm, and fast for the remaining 16 hours. During the fasting period, only water, tea, or black coffee is allowed. Healthy eating habits should still be maintained during the eight-hour eating window.

"Short-term studies indicate that people find it easier to stick to intermittent fasting than some other diets," said Dr Hu. 

"The 16/8 schedule can be easier to follow since a significant part of the fasting window occurs while you're asleep," he addes. 

Ketosis and weight loss

One potential reason intermittent fasting could help in weight loss is that it promotes short-term ketosis, a state where the body burns fat for energy after depleting glucose reserves. 

Ketosis begins when the body runs out of its preferred energy source, glucose, and starts using stored fat instead. 

Dr Hu explained, "Sixteen hours of fasting is sufficient for some people to enter ketosis or start producing ketones."

Beyond weight loss, intermittent fasting has been linked to broader health benefits. These include reducing risk factors for cardiovascular diseases such as high blood pressure, cholesterol, and blood sugar levels, as well as potentially supporting a healthier gut microbiome. Some proponents also claim intermittent fasting boosts energy levels. However, the long-term effects remain unclear. 

"Most studies on intermittent fasting have small sample sizes and focus on short durations — typically a few weeks to a year," cautioned Dr Hu. As such, while the early findings are promising, more comprehensive research is needed to evaluate its long-term impact.

A gradual start

If you're considering intermittent fasting as a strategy to manage your weight, Dr Hu suggests starting slowly. 

"A 12/12 schedule, where you fast for 12 hours and eat during the other 12, is a good way to ease into it. Then, as your body adjusts, you can gradually increase the fasting window," he advised. 

The final goal can be the popular 16/8 approach, but the transition should be slow and comfortable.

As with any diet change, it's essential to consult with a doctor, especially for individuals with certain health conditions. 

"For those with diabetes, high blood pressure, or those prone to dizziness, intermittent fasting may present some risks. Low blood sugar due to extended fasting could lead to complications," warned Dr Hu.

Consistency is key

While intermittent fasting might aid weight loss, Dr Hu emphasised that success also hinges on a balanced diet. 

"To achieve lasting results, fasting must be paired with healthy eating, portion control, and minimising processed foods," he said.

Dr Hu also stressed the importance of consistency. 

"Intermittent fasting is not a quick-fix solution. Slow, steady weight loss—about half a pound to one pound a week—is more sustainable and healthy in the long run," he added.

If you do happen to miss a day or two, don't be discouraged. 

"Falling off track occasionally doesn't negate your progress. Just return to the routine and keep going," said Dr Hu. 

Over time, intermittent fasting can become a manageable part of daily life, helping users maintain both their weight and overall health.