Jason Fung2026The sequel to The Obesity Code
Resetting Your Body's Fat Thermostat in the Age of Ultra-Processed Food
Your body has a setting for how much fat it keeps, and it defends it with hunger. Fighting the hunger rarely lasts. Fung's plan is to turn the setting down.
The core idea
Jason Fung is a Toronto kidney specialist best known for The Obesity Code and his work on intermittent fasting. The Hunger Code is his follow-up, and it moves the question from what and when you eat to why you feel hungry in the first place. He argues that the body defends a fat set point, a thermostat run by hormones such as insulin, and that ultra-processed food and constant eating push the setting up. He sorts hunger into three kinds, homeostatic, hedonic and conditioned, and answers them with three golden rules: avoid ultra-processed food, build in a regular fasting period, and redesign your surroundings and social habits. Around those rules he sets dozens of short practical tips, and he draws on research into hunger hormones and on the new weight-loss drugs such as Ozempic.
In The Obesity Code the question was insulin, and when to eat. Here Fung asks a plainer one: why am I hungry right now? His answer is that a diet which leaves you hungry is set up to fail, because the body reads the cut as a threat and pushes back until the weight returns.
So the book treats hunger as three separate signals, each with its own fix. Body hunger answers to what you eat and how often. Pleasure hunger answers to what is in the cupboard. Cue hunger answers to the places, times and people around food. Lower all three and, in Fung's view, the thermostat settles lower too.
Hunger 1 · Body hunger
The body asking for fuel. Hormones such as insulin, ghrelin and cortisol run it, and it builds slowly.
Tell: Comes on gradually. Almost any proper meal would settle it.
Hunger 2 · Pleasure hunger
Eating for the reward or for comfort. It is aimed at a taste, and it can arrive on a full stomach.
Tell: Wants something specific. A plain meal would not do.
Hunger 3 · Cue hunger
A learned urge set off by a place, a time or other people: the film, the meeting tray, the evening show.
Tell: Starts when the cue appears and fades when it goes.
Interactive · the hunger check
Next time you want to eat between meals, answer five quick questions. The dial shows which of the three hungers it most looks like and what to try. Log it, and after a few days you'll see which golden rule matters most for you.
Not medical advice. This is a reflection tool, not a diagnosis or a diet plan, and no substitute for professional care. If eating feels out of control or frightening, talk to your doctor or an eating-disorder helpline. If you are in danger, call your local emergency number.
The reading
Answer the five questions to get a reading.
Nothing logged yet. Log three or more hungers to see a pattern.
HourLife's tool, built on the three hungers and three golden rules the book describes. The questions and suggestions are ours, not Fung's. Everything stays in this browser.
Concept anatomy
In the book's model, the setting is not fixed. Some things in modern life push it up, and the three golden rules are meant to bring it back down. The left column is HourLife's summary of the pressures Fung describes.
HourLife's reading of how the rules map onto the three hungers. Fung presents them together; this grid is our way of seeing where each one does most of its work.
| Body | Pleasure | Cue | |
|---|---|---|---|
| Rule 1Avoid ultra-processed food | |||
| Rule 2Build in a fasting period | |||
| Rule 3Redesign your surroundings |
The loop the book sets out to break, in HourLife's words.
Community insights
Nº 01HourLife takeaway
Fung's starting point is that cutting food without dealing with hunger tends to make hunger louder, and most people regain what they lose. He frames this book as the sequel to The Obesity Code, with hunger itself as the thing to fix.
Nº 02HourLife takeaway
Eat less and the body can push back with more hunger and less energy spent. Fung's aim is to lower the setting rather than fight it every day. Most researchers agree the body defends its weight to some degree, but how fixed that set point is remains debated.
Nº 03HourLife takeaway
Homeostatic hunger is the body's need, run by hormones. Hedonic hunger is eating for pleasure or comfort. Conditioned hunger is set off by places, times and people. Treating all three as one problem is why a single rule rarely holds.
Nº 04HourLife takeaway
Fung contrasts cookies, which push insulin up and favour fat storage, with eggs, which raise fullness hormones such as GLP-1. In his view the hormone response matters more than the calorie count. That is his position; many nutrition researchers still treat calories as the main lever.
Nº 05HourLife takeaway
It is less filling, built to taste good, cheap and everywhere. That is why avoiding it is the first of Fung's three golden rules. Researchers broadly agree these foods make overeating easier, even where they argue about why.
Nº 06HourLife takeaway
A regular fasting period is the second golden rule. It can be as plain as not eating after an evening hour, or not eating in front of the TV. Anyone taking medicine for diabetes or blood pressure should plan this with a clinician first, because doses may need to change.
Nº 07HourLife takeaway
The cinema, the office snack table, the game on TV: none of them make the body need food, yet they reliably start the urge. Fung's third golden rule is to redesign your surroundings and your social habits so the cue stops firing.
Nº 08HourLife takeaway
Fung counts cortisol among the hormones behind homeostatic hunger. So some of the fixes for appetite are not about food at all: a late night or a hard week can show up as hunger the next day.
Nº 09HourLife takeaway
Fung's point is that weight tends to return when the drug stops, because the hunger signals come back. The book covers keeping weight steady after a fast or after coming off these drugs. Starting, stopping or tapering any medicine is a decision to make with your prescriber.
Action steps
Each time you want to eat outside a meal, note the time, where you are, and which hunger it feels like: body, pleasure or cue. The hunger check on this page keeps the tally for you.
Look at your last grocery receipt and circle the three ultra-processed items you buy most often. Pick a whole-food stand-in for each and buy that instead this week.
Choose an evening hour after which you don't eat, and tell the people you live with. If you take insulin or other diabetes medicine, agree any fasting window with your clinician before you start.
Put snacks in an opaque tin on a high shelf, clear the desk drawer, and leave the counter bare. Food you can't see starts fewer conditioned urges.
Pick one first meal built on protein and fibre, such as eggs with vegetables or beans on wholegrain toast. Write it on the fridge so the morning needs no decision.
At each meal, start with the protein and the vegetables. When you eat starchy or sweet carbohydrates, have them alongside fat and protein rather than on their own.
Before any unplanned snack, wait ten minutes and name which of the three hungers it is. If it is the body, eat a proper meal; if not, deal with the feeling or the cue.
Keep one fixed bedtime from Monday to Thursday. After a short night, expect a hungrier day and plan a filling meal instead of grazing.
Find a friend with a similar aim and swap a short message every week about the hardest cue you met and how you handled it. Talk about habits, not the scale.
Stop arguing with your hunger. Find out which kind it is, and turn the dial down instead.HourLife note after Jason Fung
Pick setup actions and daily habits from The Hunger Code: Resetting Your Body's Fat Thermostat in the Age of Ultra-Processed Food, choose a start date, and download a printable checklist with real calendar pages.
Jason Fung is a Toronto kidney specialist best known for The Obesity Code and his work on intermittent fasting. The Hunger Code is his follow-up, and it moves the question from what and when you eat to why you feel hungry in the first place. He argues that the body defends a fat set point, a thermostat run by hormones such as insulin, and that ultra-processed food and constant eating push the setting up. He sorts...
HourLife’s key takeaways include: Hunger, not willpower, decides how much you eat, so a diet that leaves you hungry is built to fail. Your body defends a fat set point the way a thermostat defends the temperature of a room. There are three hungers, homeostatic, hedonic and conditioned, and each one needs a different answer.
It's a strong pick for readers exploring How Your Body Works and Metabolic Health. HourLife distills its core idea into key insights and practical actions worth trying.
Keep a three-day hunger log — Each time you want to eat outside a meal, note the time, where you are, and which hunger it feels like: body, pleasure or cue. The hunger check on this page keeps the tally for you.
About five minutes. The HourLife summary distills The Hunger Code: Resetting Your Body's Fat Thermostat in the Age of Ultra-Processed Food into its core idea, 9 community insights, and 9 practical actions you can apply right away.
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