By Domenic Chindamo, Pharmacist - Lygon Everyday Chemist, Brunswick East

If you spend five minutes on YouTube, you’d think intermittent fasting and keto can:

• “Reset your metabolism”
• “Reverse insulin resistance”
• “Turn you into a fat-burning machine”
• “Cure everything from brain fog to diabetes to ageing”

As a pharmacist who’s spent almost four decades talking to real people about real bodies (not Instagram bodies), I want to answer one simple question:

Is intermittent fasting a safe, evidence-based way to reach a healthy weight and vitality - or mostly clever marketing?

Let’s unpack the science, the hype, the role of insulin resistance and keto, and what I actually recommend in practice.

What exactly is intermittent fasting?

“Intermittent fasting” (IF) isn’t one diet - it’s a pattern of eating that cycles between time when you eat and time when you don’t. 

Common versions:

• 16:8 - Fast 16 hours, eat in an 8-hour window (e.g. 11am–7pm).
• 5:2 - 5 days of normal eating, 2 days at very low calories (500–600).
• Time-restricted eating (TRE) - Eat all your calories within 8-10 hours each day.
• Alternate-day or 4:3 fasting - Very low calories on 3 days per week, normal eating on the others.

In most studies, total weekly calories are still reduced - fasting is just a different way to create that calorie deficit.

Does intermittent fasting actually work for weight loss?

What the big reviews show

• An umbrella review of multiple meta-analyses (lots of trials bundled together) found that IF does reduce weight, BMI and some cardiometabolic risk factors in adults with overweight or obesity - but its benefits are generally similar to continuous calorie restriction, not dramatically better.
• A 2024 review comparing different IF styles found all of them modestly improved weight, waist size and insulin resistance compared with doing nothing - but were not clearly superior to standard calorie-restricted diets.

So, in plain English: IF works for weight loss for many people. It’s not a miracle, but it can be a very practical structure for eating less overall.

Newer trials – is it better than daily calorie cutting?

A recent 12-month randomised trial (4:3 intermittent fasting vs daily calorie restriction) found:

• Both groups were aiming for the same weekly energy deficit.
• The fasting group lost about 50% more weight (around 7.7 kg vs 4.8 kg).
• Drop-out rates were lower in the fasting group.

Why? Probably because some people find “don’t eat much today” easier than “eat a bit less every day forever”. But this is still moderate weight loss - not 20kg in a few months - and results will vary between individuals.

Insulin resistance: where fasting really makes sense

What is insulin resistance?

Insulin is the hormone that helps move glucose from your blood into your cells. Insulin resistance means your cells are “hard of hearing” to insulin’s signal, so your pancreas has to pump out more insulin to keep blood glucose in range. 

Over time this can lead to:

• Higher fasting insulin and glucose
• Fatty liver
• Type 2 diabetes
• Increased cardiovascular risk

Weight gain around the middle, low activity and highly processed diets all play a role.

How does intermittent fasting help?

Several human trials show that IF - especially time-restricted eating - can:

• Reduce body weight and visceral fat
• Improve insulin sensitivity
• Improve markers like fasting glucose and insulin in people with type 2 diabetes or insulin resistance

Some studies suggest early-day eating windows (e.g. 7am–3pm) may have extra metabolic benefits because they align better with our body clock. However, when you match the calorie deficit, IF is often no better than “regular” calorie restriction - it’s just another way to achieve it.

So: IF can improve insulin resistance, mostly by helping people lose fat and eat less overall. The “magic” is lower calories and better timing, not a mysterious detox switch.

Where does keto fit in?

What is a ketogenic (keto) diet?

A classic very-low-carb ketogenic diet (VLCKD) usually means:

• Less than 50g carbs/day, sometimes up to 50-100 g in “liberal” low-carb plans
• Higher fat, moderate protein

Evidence: short-term benefits, open questions long-term

Recent meta-analyses and clinical trials show that low-carb and keto diets:

• Reduce body weight, BMI and body fat percentage
• Often improve triglycerides, HDL and HbA1c in people with metabolic syndrome or type 2 diabetes
• In some studies, can reduce the need for diabetes medicines (under medical supervision)

BUT:

• LDL cholesterol can increase in some people, particularly with very high saturated fat intake.
• We have less long-term data (5-10 yrs+) on hard outcomes like heart attacks, stroke and mortality.
• It can be socially and culturally restrictive, and many people struggle to stay on strict keto.

Diabetes Australia notes that low-carb eating can be a valid option for some people with diabetes, but should be done with professional support because medicines (especially insulin and sulfonylureas) often need dose changes.

Intermittent fasting + keto = super hack?

Some YouTube doctors recommend combining IF and keto, arguing that:

• Less insulin from low carbs plus fasting equals “turbo fat burning”
• You’ll be in deep ketosis, reversing insulin resistance and inflammation

Physiologically, it’s true that:

• Low carbs and fasting both lower insulin levels
• Lower insulin promotes lipolysis (fat breakdown) and ketone production

But here’s the key point:

The main driver of fat loss is still overall energy deficit and adherence – not the exact ketone reading on your breath meter. For some people, keto + IF feels great and they naturally eat less. For others it’s a fast track to:

• Cravings
• Binge episodes
• Social isolation (“I can’t eat anything at Nonna’s house now”)

Fact or Fiction? Common YouTube Claims

“Intermittent fasting melts fat even if you eat whatever you like.”

Mostly fiction. Many trials show that when people eat ad lib on non-fasting days, they still tend to eat less overall - but total calorie intake still matters.

“IF reverses insulin resistance.”

Partly true. Studies show improved insulin sensitivity and b-cell function, particularly in people with overweight or early diabetes. But it’s not guaranteed and usually tied to fat loss and better food quality.

“It detoxes your body.”

Fiction. Your liver and kidneys do detoxing 24/7. Fasting may promote cellular “clean-up” (autophagy) in animals, but human evidence is early and not a licence for extreme fasting.

“IF will make you live to 120.”

Unproven. Animal data on fasting and longevity are interesting, but we do not have long-term human trials showing big life-extension benefits yet. We do have modest improvements in risk factors like weight, BP, lipids and insulin - which might reduce long-term risk.

The real-world risks: what’s the harm?

Most trials in adults with overweight/obesity show IF is generally safe in the short to medium term (months to a few years) when done sensibly. But real life isn’t a clinical trial. Short-term side effects & common issues include:

• Hunger, headaches, irritability, “brain fog”
• Sleep disturbance
• Heartburn from large meals in short windows
• Social stress (“I can’t eat at that time”)

Disordered eating risk

Psychologists and eating disorder programs warn that rigid fasting patterns can trigger or worsen disordered eating, particularly in people with a history of dieting or body-image concerns. 

People who need to be especially careful or avoid IF without specialist advice

• Type 1 diabetes, or type 2 diabetes on insulin/sulfonylureas (risk of hypos, DKA) – Australian diabetes guidelines for Ramadan fasting highlight these risks clearly.
• Pregnant or breastfeeding women
• Children and teenagers
• People with eating disorders or a history of them
• Frail older adults or those with chronic illness
• People on medicines that require food at set times

For these groups, fasting should only be considered with close medical supervision - if at all.

Pros & Cons at a glance

Potential pros of intermittent fasting

• Helps many people naturally reduce calories
• Clear rules: easier than counting calories for some
• Modestly improves weight, waist size, triglycerides, insulin resistance in trials
• Can align with circadian rhythms (early eating windows)
• Works with many dietary styles (Mediterranean, plant-based, lower carb, etc.)

Potential cons of intermittent fasting

• Not inherently better than any other evidence-based diet when calories are matched
• Can backfire into binge-restrict cycles
• Hard with shift work, family life, social meals
• Risky for people with diabetes, eating disorders, pregnancy, etc.
• Can be used as a “quick fix” distraction from sleep, stress, movement and ultra-processed food intake – which matter just as much.

Potential pros of keto/very low-carb

• Rapid improvement in blood glucose and triglycerides in many people
• Effective for short-term weight loss
• Some people feel fewer cravings and more stable appetite

Potential cons of keto/very low-carb

• Possible LDL cholesterol rise in some
• Hard to sustain socially and culturally
• Nutrient gaps if poorly planned
• Needs medicine review in diabetes and some other conditions
• Very restrictive versions can be risky without professional oversight

What do I believe as a pharmacist?

After almost 40 years in pharmacy, talking to patients in Brunswick East every day, here’s my honest view:

1. Intermittent fasting is a tool, not a miracle.

It can absolutely help some people lose weight, improve insulin resistance and feel more energetic - if it helps them eat better overall and stick with it.

2. The “boring” basics still matter more than the timing window.

• Lots of vegetables, fibre and whole foods
• Adequate protein
• Mostly unsaturated fats (olive oil, nuts, avocado, fish)
• Sleep, stress, movement, connection

3. The best eating pattern is the one you can live with for years, not weeks.

For many of my patients, a gentle approach like:

• Start with 12:12 (12 hours eating, 12 hours fasting overnight)
• Move slowly to 14:10 if it feels good
• Combine it with a mostly Mediterranean-style pattern gives far better long-term results than jumping straight into hardcore OMAD (one meal a day) or extreme keto.

4. If you have diabetes, heart disease, are on multiple medicines or have a complex medical history - don’t do this alone.

In Australia, we also have TGA-approved medicines (like GLP-1 agonists) that can be part of a structured program for some people. Those decisions should be made carefully with your GP, specialist and pharmacist - and always alongside lifestyle changes, not instead of them.

5. YouTube doctors are useful for ideas, not prescriptions.

I love that people are curious and motivated. But your body, your medicines and your life are not a click-bait thumbnail. What works “perfectly” for a 35-year-old fitness influencer might be dangerous for a 62-year-old with diabetes and blood pressure tablets.

So..does the system perform?

Short answer:

Yes, intermittent fasting and (for some) low-carb or keto can be safe and effective, evidence-based tools for weight loss and metabolic health - but they’re not magic, and they’re not for everyone.

• The proof: multiple randomised trials and meta-analyses show modest but real benefits for weight, insulin resistance and cardiometabolic risk factors.
• The performance: in the real world, it works best when it fits your lifestyle, culture and medical needs.
• The purpose: not just a smaller number on the scale, but better energy, lower long-term risk and a way of living you can enjoy.

My suggestion if you’re curious

Before you try intermittent fasting or keto:

• Chat to your GP and pharmacist (especially if you’re on medicines).
• Consider starting with:
• A consistent overnight fast (12–13 hours)
• Cutting back ultra-processed foods and sugary drinks
• Building a realistic movement plan you can enjoy

If you’re local to Brunswick East, you’re always welcome to pop into Lygon Everyday Chemist and we can chat through medicines, supplements, monitoring and which style of eating might suit your body - not YouTube’s idea of it.