Dr Nick Fuller
Leading Obesity Expert at the University of Sydney and founder of Interval Weight Loss.
When it comes to diets and weight loss, intermittent fasting (IF) has been the cool kid on the block for a while now, and it’s not just hype. Beyond skipping breakfast or having dinner early, IF could actually help give your metabolism a gentle nudge in the right direction.
But how does it really work? Let’s break it down and see what science says.
Let’s start with the basics: your metabolism is the engine that keeps your body ticking. It’s responsible for turning the food you eat into energy. Intermittent fasting doesn’t magically rev it up like a sports car, but it does tweak some key hormones that affect how you burn fat and store energy.
Research shows that during fasting periods, your body switches from using glucose (sugar) to burning fat as fuel. A study suggested that intermittent fasting can reduce body weight and improve metabolic health, even without cutting calories too much.
Thinking about trying intermittent fasting the right way—without wrecking your metabolism? Check out how Interval Weight Loss makes it sustainable, not stressful.
Intermittent fasting is more than just about skipping meals. It flips a few important metabolic switches behind the scenes. Below shows how it happens:
When you fast, your insulin levels drop and your body starts dipping into stored fat for energy. Think of it as your body finally using the snacks it’s been hoarding in your love handles.
Insulin is like your body’s fat-storing switch. Lower insulin equates to less fat storage. Studies have found that intermittent fasting can significantly reduce insulin levels and improve insulin sensitivity. It means your body becomes more efficient at using stored energy.
Fasting significantly increases human growth hormone (HGH) levels. One study showed a more than threefold rise in just five days. HGH plays a key role in fat loss and muscle maintenance, which is a nice bonus if you’re trying to tone up as well as slim down.
Let us take a closer look at the metabolic dream team working behind the scenes:
Lower levels of insulin mean your body gets better at breaking down fat for fuel. It’s a bit like your body going from hoarding mode to fat-burning mode.
This hormone does a bit of everything—helps build muscle, burn fat, and even slow down ageing. During fasting, HGH surges, giving your metabolism a solid kick.
This one’s your body’s natural stimulant. When you fast, norepinephrine ramps up, helping break down body fat into free fatty acids. Basically, it turns your fat into usable fuel.
You don’t have to go full caveman to try intermittent fasting. Here are some popular approaches:
This one’s a fave. You fast for 16 hours and eat all your meals within an 8-hour window. For example, you might eat between 12 pm and 8 pm—that simple.
Eat normally five days a week, and then eat only around 500–600 calories on the other two days. It’s less about meal timing and more about cutting intake twice a week.
As the name suggests, you fast every other day. Some people do full fasts, while others have a very low-calorie intake on fasting days. It’s not for everyone, but some find it effective.
There’s more to intermittent fasting than just metabolism perks. Below are some of the other feel-good side effects:
The combo of fewer meals and better fat-burning hormones usually leads to weight loss. A study found that intermittent fasting could result in a 3–8% weight loss over 3–24 weeks.
Intermittent fasting helps your body use glucose more effectively, which is great news if you’re watching your blood sugar levels. One study showed it improved insulin sensitivity and glucose tolerance.
Some studies suggest intermittent fasting lowers markers of inflammation, which is linked to better long-term health and a lower risk of chronic disease.
Fasting may help reduce blood pressure, cholesterol, and triglyceride levels—aka the major players in heart health.
So, does intermittent fasting help metabolism? Absolutely—by adjusting hormone levels, encouraging fat burning, and supporting better metabolic health overall. But it’s not about starving yourself or skipping every meal. It’s about working with your body, not against it.
If you’re keen to try intermittent fasting but don’t want to fall into the yo-yo trap, Interval Weight Loss has a science-backed plan that helps you lose weight and keep it off—for good. No extreme fasting. Just real results.
Dr Nick Fuller is the founder of Interval Weight Loss and is a leading obesity expert at the University of Sydney with a Ph.D. in Obesity Treatment. Dr Fuller is also the author of three best-selling books and his work been published in top ranked journals in the medical field, including JAMA, Lancet and American Journal of Clinical Nutrition.