What Is The Best Intermittent Fasting Window To Lose Belly Fat In 2023?

Obesity affects a significant portion of our population, putting more people at increased risk for chronic diseases, such as cardiovascular disease, difficulties with metabolic health, and insulin resistance. An abundance of weight-loss diets promise fat loss with resulting positive health benefits, but more people are looking to intermittent fasting for weight loss and fat burning. 

Intermittent fasting (IF) has been around for many years as a form of religious worship, but the diet recently sparked new popularity as a perceived way to lose unwanted body weight. However, many people wonder if it can specifically help you in losing belly fat. This article will explore the ins and outs of intermittent fasting and the possible role of IF in getting rid of stubborn belly fat. The need for further human research is emphasized. 

What Is The Best Intermittent Fasting Window To Lose Belly Fat?

The effects of meal timing are not limited to IF diets. Our bodies respond to meals and snacks differently throughout the day in nutrient metabolism and hormonal balance, so it’s no surprise that our bodies would react differently to various fasting periods. 

There is still a need for continued research regarding the ideal fasting window, but one recent study^[1] found weight loss success when participants fasted for 14 hours and ate during the remaining 10 hours. Another study^[2] found similar weight trends for participants who fasted for 16 hours versus 12 hours but found that those who fasted for 16 hours actually had lower insulin levels, reduced insulin resistance, and lower blood pressure. Another review of studies^[3] showed no difference in weight loss or waist circumference between the IF regimens of 16:8 or alternate-day fasting.

Researchers are actively testing the science behind time-restricted eating, but there is still much to learn about fasting and if it can play a role in a healthy diet. Each person has individualized needs making it difficult to determine the best intermittent fasting to lose belly fat.

Important Consideration

One thing often neglected in considering an IF pattern is the time of day the fasting window occurs. With nutrients, there is a circadian rhythm in metabolism, and the metabolism is greatest during the day, which is when the eating window should occur. A circadian rhythm diet^[4] has an eating window from 7 am – 7 pm to allow for caloric intake when metabolism is high and more calories are metabolized due to high thermogenesis. But this fasting window could easily be adjusted to a 16-hour fast with eating restricted to 11 am – 7 pm to achieve similar positive metabolic effects on reducing belly fat while working with your circadian rhythm.

Another important consideration is the effect or consequence of lifting the diet restrictions once you’ve reached your weight goal. Returning to a normal diet, despite continuing your exercise, may result in weight gain or other health concerns. In reality, the long-standing tried and true solution for successful weight loss or weight maintenance continues to be the balance between energy intake and energy output and paying attention to the time of day you are eating. Late-night eating generally results in weight gain secondary to the circadian rhythm in hormones, including appetite hormones such as leptin and the rhythm of nutrient metabolism.

If you have health concerns about your weight or weight distribution, consider meeting with your primary healthcare provider or registered dietitian nutritionist before starting any dietary restrictions. Pregnant and breastfeeding women should avoid these diet restrictions, as should people with a cancer diagnosis. Lastly, people with a history of disordered eating should not implement these severe restrictions.

What Is Intermittent Fasting?

Intermittent fasting is an eating pattern that alternates between calorie restriction and normal energy intake. With IF, there are no restrictions on the types or amounts of food you eat during your eating window, but rather your day’s food intake is time restricted to an eating window alternating with a fasting window. 

Intermittent fasting is based on the idea that our hunter-gatherer ancestors survived for great lengths of time between successful hunts and harvests. IF is more than a skipped meal or two. It tells us that our bodies can survive on limited or no energy intake for certain periods of time.

During your belly fat intermittent fasting window, you are to avoid calorie intake of any kind. Once outside of your fasting period, you’re allowed to eat your everyday foods and portion sizes. 

In reality, by assigning yourself an eating window, you naturally consume fewer calories in the day, which ultimately helps you lose weight. That is unless you overcompensate and consume more calories during your eating periods than your body burns during the day. 

Types Of Intermittent Fasting

There are multiple methods of IF, each with its own ratio of eating versus fasting. Some of these methods include:

• The 5:2 Method, in which you consume minimal calories (500-600 calories) for two nonconsecutive days of the week and then eat your normal intake for the remaining five days. 
• The Eat Stop Eat Method requires you to completely abstain from eating on two nonconsecutive days of the week and then consume your normal intake during the remaining five days.
• The 16/8 Protocol only allows you to eat within an eight-hour window each day, and you must fast for the remaining 16 hours of the day.
• Alternate Day Fasting allows you to eat normally one day but then requires you to fast on the following day. The alternate-day pattern continues for the entirety of the time-restricted diet. 

In addition to the benefits of intermittent fasting for weight loss, researchers have found that IF diets can lower blood pressure, improve blood sugar control, decrease inflammation, and improve brain function. However, there is still room for continued research on IF and its impact on specific chronic diseases.

Can You Use IF To Get Rid Of Belly Fat?

We’re seeing health trends focus more on our overall wellness than our physical appearance like in years past. So when we talk about belly fat, we’re really talking about more than the obvious subcutaneous fat; rather, we are referring to visceral fat, which gathers around our abdominal organs. 

You can’t always see it from the outside. Still, science has shown an association between visceral fat and an increased risk of chronic diseases such as heart disease, type II diabetes, Alzheimer’s disease, and elevated cholesterol. Research suggests that visceral fat makes more of the proteins and hormones that are responsible for the inflammation in our body’s tissues and organs. 

So, it’s understandable to want to reduce your belly fat when you have your overall health in mind. But can you follow an intermittent fasting journey to lose visceral fat? The answer is yes and no. Visceral fat is resistant to IF attempts at weight loss^[5] in animal models, suggesting that more human research is needed to determine actual effects. The visceral fat may develop a “starvation mode,” making it resistant to fasting diets.

IF is believed to aid in weight loss, but just like any other diet, the main component behind fat loss is daily calories in versus daily calories out. So while IF can help you lose weight, it is not a targeted weight-loss program designed for just one specific area of your body.

Does It Burn Belly Fat?

You burn fat by creating a calorie deficit during IF and using fat for fuel, so if you consume fewer calories than you expend, you will see a loss of body fat and an accelerated burning of fatty acids. Unfortunately, according to many studies, there is no way to “spot treat” specific body fat. Losing visceral fat will occur in conjunction with overall body fat loss, just like any other temporary diet. Along with the debate on the spot treatment, other research has shown^[6] a greater loss of waist circumference with IF than with calorie restriction alone. Apparently,  more research is needed in this area, particularly with humans.

A recent review of studies^[7] found a correlation between IF and weight loss. For example, one study found that participants had a 3-4% reduction in body weight over 2-3 weeks of intermittent calorie restriction. When the time frame was extended, participants lost 5-8% of their body weight while fasting for 8-12 weeks.

Suppose you plan to try IF, and your goal is to lose weight and build lean muscle mass safely. In that case, it’s crucial to maintain healthy habits such as exercise, getting enough sleep, consuming adequate calories and protein during your eating window, and staying hydrated at all times. Fat burning cannot come at the cost of other areas of health if you wish to maintain your weight loss, muscle mass, and visceral fat loss. 

Final Thoughts

While the research behind IF and belly fat reduction is controversial and more human research is needed, there have been enough studies to warrant trying IF to lose stubborn belly fat. While there are many factors to consider in choosing an IF regimen, choosing a fasting window that optimizes your circadian rhythm would seem most beneficial, and considering a comprehensive lifestyle approach to reducing your belly fat is the optimal route. The combination of an exercise program, healthy eating during your eating window, and achieving good sleep are all lifestyle practices that can assist IF in helping you lose your abdominal girth.

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