Have you noticed how fasting advice only ever goes in one direction? Sixteen hours becomes twenty-four. Twenty-four becomes alternate days. Before long someone in a forum is doing a week. If fasting is good, surely more of it is better?
I had a conversation on the podcast with Marty Kendall that reframed this for me. Marty is an engineer by trade with no formal nutrition qualifications, and he says so cheerfully — but he has spent close to twenty years reading the scientific literature and tracking data, which began when he set out to help his wife manage type 1 diabetes. That origin story matters, because it is why he thinks in numbers rather than slogans. And his conclusion on fasting is the opposite of what most of the internet will tell you.
The minimum effective dose, not the maximum
Marty's engineering instinct is to ask: what is the smallest amount of an intervention that gets the result you want? Applied to fasting, that question reveals how little most of us have actually thought this through.
Take autophagy — the cellular clean-up process everyone cites as the reason to fast harder. Marty's point is that much of the eye-catching research is in mice, and that a day in a mouse's life is not a day in yours. Scaled across lifespans, replicating a mouse study's fasting window in human terms would mean an extraordinarily long fast. I would not want to put a precise number on the conversion, and nor should anyone — but that is rather the point. The autophagy argument is used with far more confidence than the evidence supports.
His own week-long fast taught him something more useful than any biomarker. By the end he was so hungry he would eat anything, and his "lizard brain" had thoroughly convinced him he had earned it. His wife eventually observed that this did not appear to be working out for him. If your fast ends with you eating the contents of the fridge, you have not come out ahead.
Using hunger as information, not an enemy
Here is where his approach is genuinely interesting. Rather than overriding hunger with willpower, he uses a simple measurement to check it. If your blood glucose is still sitting up, you have fuel on board and the hunger may be something other than a need for energy. If it has dropped properly, eat — and eat normally.
The real value, he says, is not the number. It is the pause. Asking "am I hungry enough to actually test this?" interrupts the automatic reach for food long enough for you to think. And within weeks most people can predict the reading from the sensation, which means they have relearned their own hunger signals. That is the actual goal.
A caution from me, which I want to be clear about. This method came out of a diabetes context, where glucose monitoring is routine and medically supervised. Finger-prick testing to decide when to eat is not something I would suggest to everyone, and I would actively steer away from it if you have any history of disordered eating or obsessive tracking, or if you are on glucose-lowering medication. Please discuss it with your doctor or dietitian first. The underlying principle — pause and ask what the hunger actually is — costs nothing and needs no equipment.
Because hunger is often not about fuel at all. Marty talked about how readily the modern world hijacks our reward system: the endless scroll, the chronic stress, the advertisement that arrives precisely when you are tired. Food becomes soothing rather than nourishing, and the two sensations get very hard to tell apart.
The real risk of fasting harder and harder
This is the part of the conversation I most want people to hear, because it is a genuine health risk dressed up as discipline.
If you keep extending your fasts, you eat less protein. Eat less protein for long enough and you lose lean muscle. Lose muscle and your metabolic rate falls, which means you have to eat even less to see the same result. It is a descending spiral, and it ends in one of two places: a rebound binge, or a frail body with poor strength and balance in later life — which is a serious matter for fall risk and independence.
Marty noted that a lot of the people most drawn to extreme fasting are middle-aged women, who in his view need the opposite: to be robust, strong and well-fed with adequate protein. He described the end point of over-fasting bluntly — cold, tired, stalled, and having lost muscle mass that is genuinely hard to rebuild. I see exactly this in my clinic.
Prioritise protein, don't just pile it on
So protein matters. But Marty is equally wary of the other extreme, where people hear "high protein" and leap from one end of the spectrum to the other.
He pointed to the protein leverage hypothesis — work from researchers at the University of Sydney suggesting that we keep eating until our protein needs are met. If your meals are low in protein, you will simply keep eating. That explains a great deal about why people overeat energy-dense food without feeling satisfied.
His practical framing is prioritised protein rather than high protein. Start from what you already eat. Put protein first at every meal. Then look honestly at where the extra energy from fat and carbohydrate is sneaking in — he gave the example of a nutritionist who discovered she was drinking several hundred calories of cream in her coffee each morning without registering it. He offered figures of roughly 1.8g of protein per kilogram of body weight as a working target, with most people sitting far below that. I would treat those as rules of thumb rather than prescriptions; requirements genuinely vary with age, activity, body composition and kidney health.
Nutrient density is what actually satisfies you
Marty's other long-running interest is nutrient density: fitting all the amino acids, vitamins, minerals and essential fats your body needs inside your available energy. His argument is that satiety is largely about adequacy. We keep seeking food until we have enough protein, enough sodium, potassium, calcium and the rest. Give the body what it is looking for and the seeking stops.
Which is why, as he put it, it is very hard to overeat a bulky, nutrient-dense, protein-forward meal, and very easy to keep eating things engineered to hit all the right notes while delivering little. On that point he was refreshingly neutral about food ideology — vegan, omnivore or carnivore, the question is the same: am I getting the nutrients I need without excessive energy? If you eat plant-based, you just need to be more deliberate about it, because plant proteins generally arrive packaged with more carbohydrate energy.
Key takeaways
- Ask what the minimum effective dose of fasting is for your goal, rather than assuming longer is better.
- If your fast ends in an all-you-can-eat rebound, it has not worked. That is information, not a willpower failure.
- Pause before eating and ask whether it is fuel you need, or comfort, or just a habit cue.
- Protect your muscle. Extending fasts while under-eating protein costs you lean mass, metabolic rate and long-term strength.
- Prioritise protein at every meal rather than overhauling your whole diet overnight.
- Track where hidden energy is creeping in — the cream, the oils, the extras you never count.
- Aim for half a percent to one percent of body weight per week at most. Slower is the version you can sustain.
- See eating as nourishing yourself, not depriving yourself. That distinction is the whole game.
What I love about this conversation is how unglamorous the conclusion is. No heroics, no extreme protocols, no suffering as proof of commitment. Just: eat enough of the right things, pay attention to real hunger, protect your muscle, and go slowly enough that you are still doing it in a year. That is exactly how I work with clients at me&my wellness — looking at the whole person, including your sleep, your stress and your relationship with food, because an approach that only works while you are white-knuckling it is not really working.
None of this is personal medical or dietetic advice. If you have diabetes, take any medication that affects blood sugar, are pregnant, or have a history of disordered eating, please do not take up fasting without talking to your doctor first.
Want to go deeper on this? Book a free 30-minute discovery call with Anthony at meandmywellness.com.au