Written by Martin Ebner
Updated September 2026
Intermittent fasting has been through the full fitness-industry cycle. First it was ancient wisdom, then a fat-burning revolution, and before long it was apparently the secret to living forever.
It’s none of those things. It’s an eating schedule.
That might sound less exciting, but it also makes intermittent fasting much easier to understand and use properly. For some people, a defined eating window removes decisions, cuts down on mindless snacking and makes controlling calories feel surprisingly straightforward. For others, it creates little more than hunger, irritability and an impressive ability to think about lunch.
THE SHORT ANSWER
Intermittent fasting can help you lose fat, but it doesn’t bypass the basic rules of energy balance. It works when the eating schedule helps you consume fewer calories than you burn.
You don’t need to fast for sixteen hours before your body remembers it has fat stored. You don’t have to empty every gram of glycogen before fat can be used for energy, and skipping breakfast doesn’t automatically place you in a metabolic wonderland.
The useful question isn’t whether intermittent fasting works. It’s whether it makes eating well and controlling your calorie intake easier for you.
WHAT INTERMITTENT FASTING ACTUALLY IS
Intermittent fasting controls when you eat rather than prescribing exactly what you eat. The most common versions include:
12:12, with twelve hours of eating and twelve hours without food
14:10, which shortens the eating window without making the day particularly difficult
16:8, usually achieved by eating a later breakfast or an earlier dinner
5:2, with normal eating on five days and heavily restricted calories on two
Alternate-day fasting, where low-calorie or fasting days alternate with normal days
One meal a day, commonly called OMAD
None of these methods guarantees a decent diet. You can eat eight hours’ worth of nutritious food or eight hours’ worth of absolute rubbish. The clock won’t make that decision for you.
HOW INTERMITTENT FASTING HELPS WITH FAT LOSS
The main advantage is structure. When you remove several hours of eating from the day, you remove several opportunities to consume calories. That can mean fewer snacks, fewer late-night raids on the kitchen and less time spent deciding whether you’re genuinely hungry or simply bored.
A major 2025 review of 99 randomised trials found that intermittent-fasting strategies and continuous calorie restriction both reduced body weight compared with eating without restrictions. Overall, the differences between fasting and an ordinary calorie-controlled diet were small.
That’s hardly the metabolic revolution we were promised, but it’s still useful. If two methods produce similar results, the better one is the one you can follow without making your life miserable.
DOES FASTING MAKE YOUR BODY BURN MORE FAT?
While you’re fasting, insulin levels fall and your body tends to use a greater proportion of fat for energy. That part is true.
What often gets missed is that burning more fat during a particular part of the day doesn’t automatically mean losing more body fat over several weeks. Your body constantly switches between carbohydrates and fat according to what you’ve eaten, what you’re doing and how much energy you need.
Body-fat loss depends on the overall balance. If you burn more fat during the morning but replace all those calories during the eating window, the fast hasn’t created a fat-loss advantage.
It’s the same distinction I make when discussing fasted cardio and fat burning. Using more fat during a workout and losing more body fat aren’t necessarily the same thing.
IS FASTING BETTER THAN A NORMAL CALORIE DEFICIT?
Usually, no.
In a controlled trial where calories were kept the same, time-restricted eating didn’t produce greater weight loss than a conventional eating pattern. When energy intake is genuinely equal, the supposed metabolic advantage becomes difficult to find.
That doesn’t make intermittent fasting pointless. It means its value is practical rather than magical. If a shorter eating window helps you maintain a calorie deficit with less effort, it’s doing its job.
If you spend the entire fast dreaming about food and then eat everything that isn’t nailed down, it probably isn’t the right tool for you.
WHAT ABOUT INSULIN?
Insulin rises after you eat and falls between meals. That’s normal physiology, not evidence that every sandwich is blocking fat loss.
Lower insulin levels during a fast allow more stored fat to be released and used for energy, but you don’t need insulin to remain low all day to lose body fat. People lose fat while eating carbohydrates, eating breakfast and spreading meals across the day, provided their overall calorie intake supports it.
The internet turned insulin into a villain because villains sell diets. In reality, the body is considerably more complicated and far less dramatic.
DOES INTERMITTENT FASTING IMPROVE HEALTH?
It can improve markers such as body weight, blood pressure and blood-glucose control, particularly when it helps someone lose excess body fat. However, many of these benefits are also seen with ordinary calorie restriction.
Claims that intermittent fasting slows ageing or extends human life deserve far more caution. Animal studies are interesting, but mice living longer under tightly controlled laboratory conditions doesn’t prove that skipping breakfast will add years to your life. A recent assessment of fasting and human longevity concluded that the evidence remains uncertain.
Use intermittent fasting because it suits your lifestyle, not because someone has promised you immortality before lunch.
WHICH FASTING METHOD SHOULD YOU USE?
Start with the least aggressive version that achieves what you need.
A twelve-hour overnight fast is barely a diet. Finish dinner at 8 pm, eat breakfast at 8 am, and you’re there. Moving to 14:10 can reduce evening snacking or delay breakfast without completely rearranging your day.
The popular 16:8 method can also work well, particularly if you’re naturally less hungry in the morning. There’s nothing sacred about sixteen hours, though. Fifteen isn’t a failure and seventeen doesn’t earn bonus points.
The 5:2 diet and alternate-day fasting create a larger divide between restricted and normal days. Some people enjoy that separation, while others compensate by overeating when the fast ends. OMAD can make it unnecessarily difficult to consume enough protein, fibre, vitamins and minerals in a single sitting.
HOW TO MAKE INTERMITTENT FASTING WORK
Choose an eating window that fits your actual life. If dinner with your partner, family or friends matters to you, don’t choose a plan that expects you to stop eating at 4 pm. A diet that makes you avoid everyone you like isn’t particularly sustainable.
Eat proper meals when the window opens. Include protein, vegetables or fruit, a sensible source of carbohydrates and enough dietary fat. You don’t need to break the fast with MCT oil, collagen powder or some ceremonial bowl of expensive berries.
Make protein a priority, especially if you’re losing weight and strength training. Your eating window still needs to contain enough opportunities to reach your daily target. The details are covered in how to time protein intake for strength and muscle.
Keep the calorie deficit sensible. Fasting for most of the day doesn’t mean dinner should resemble the closing stages of an eating competition.
WHEN SHOULD YOU TRAIN?
Train when you feel and perform best.
Some people enjoy walking, easy cardio or a short workout before breakfast. Others feel flat, weak and thoroughly unimpressed with the experience. Neither response says anything profound about your discipline.
If you’re doing a demanding strength session, eating beforehand may help you train harder. That matters because maintaining performance gives your body a reason to retain muscle while you lose fat.
If fasted training feels good, use it. If your strength collapses and every set feels dreadful, eat something. The workout matters more than winning an argument with the clock.
WHAT BREAKS A FAST?
Anything containing meaningful calories technically ends a strict fast. That includes MCT oil, collagen, protein powder, amino-acid drinks and the mysterious “fasting supplements” conveniently sold by people explaining that food is the problem.
Water, plain tea and black coffee contain few or no meaningful calories and are commonly used during fasting periods.
For fat loss, this doesn’t need to become a purity contest. A small amount of milk in your coffee won’t erase a calorie deficit or stop your progress. If it makes the routine easier to follow, the practical benefit probably matters more than technically maintaining a flawless fast.
WHO SHOULD BE CAREFUL?
Intermittent fasting isn’t appropriate for everyone. Speak to a qualified healthcare professional before fasting if you’re pregnant or breastfeeding, underweight, frail, recovering from illness, managing an eating disorder or taking medication that’s affected by food intake.
People using insulin or certain diabetes medications need particular care because fasting can increase the risk of low blood sugar. The National Institute of Diabetes and Digestive and Kidney Diseases advises that medication changes and fasting should be managed with professional guidance rather than attempted alone.
If you’re taking weight-loss medication such as semaglutide or tirzepatide, don’t automatically pile aggressive fasting on top. These medicines already reduce appetite, and you still need sufficient protein, nutrients and fluids. Current UK guidance on GLP-1 medicines stresses medical supervision, good nutrition and proper hydration.
FASTING IS A TOOL, NOT A TEST OF DISCIPLINE
Intermittent fasting can be a perfectly sensible way to control calories and lose fat. It can also be completely unnecessary.
If delaying breakfast simplifies your day and helps you eat better, carry on. If it leaves you hungry, antisocial and thinking about food from the moment you wake up, choose another approach. You don’t receive a medal for reaching lunch without eating.
I don’t care whether you call it intermittent fasting, time-restricted eating or simply missing breakfast. What matters is whether it helps you build a routine you can maintain.
If you want a plan built around your training, lifestyle and actual appetite, rather than someone else’s fasting clock, you can read about my weight-loss coaching in Barcelona.
If your nutrition plan has started requiring a stopwatch, a ketone meter and a minor qualification in biochemistry, Check It Oot is where I strip fitness and nutrition back to the useful stuff. One email once or twice a month, written by me, straight to your inbox.
