The flat line.
In Canada, a continuous glucose monitor, a CGM for short, is hard to get if you do not have diabetes. Insurance covers it for people who do. It is a small sensor that sticks to the back of your arm, reads your blood sugar every five minutes, day and night, and sends it to your phone. The ones I bought were good for ten days, and they talk to Dexcom's own free app.
I found someone on Marketplace selling five of these sensors. I bought all five. They come with an expiration date, about three months out. A friend took three, and I kept two. I did not need one. I had no reason to think I had an issue with sugar. But the curious alchemist in me wanted to see how my body actually handles it, and to test it against different kinds of food.
I wore the first one in November and kept eating normally. My line did not budge at all. So I saved the second one for the holidays, when most of us indulge. I put it on in Montreal the day before Christmas, knowing I would finish it in Sint Maarten, where I spend New Year's and a chunk of every winter.
I call myself a professional foodie. I live to eat, I do not eat to live, and my friends know my obsession with food. A party I hosted just before Christmas left me with the leftovers of two big cakes, and I worked my way through them all week. Christmas family dinner was a lamb roast, potatoes, a bunch of other sides and wine, with carrot cake, tiramisu and fruit for dessert. New Year's Eve in Sint Maarten was also a feast. It started at a Brazilian churrascaria I had helped a friend open there: beef, chicken, lamb and every other meat they carry around on skewers, side dishes covering the table, dessert and wine. For the midnight countdown, I went to another friend's house, with a lot more drinking. I was on holiday and I indulged. I know exactly what I ate because back then I logged every meal in a fasting app.
The line stayed flat. My average over both sensors was 5.0 mmol/L, which is 90 mg/dL in American units, and I never came close to the high line on the screen. Two sensors, twenty days, including ten days of holiday indulgence, and not one spike.
This piece is what I found when I went looking for why. By the end you will know what a spike actually is, what it does to the fat on your body, how a run of them can lead to diabetes, why my line stayed flat, and the three habits that research shows move the line. No pills, no powders.
The spike goes viral.
Ten years ago almost nobody outside a diabetes clinic talked about glucose. Now people post about their blood sugar.
Many people know about glucose spikes because of the longevity trend and two viral accounts in particular. The first is Justin Richard, a creator from Toronto with about two million followers on Instagram, who goes by Insulin Resistant 1. His videos are short: he tests foods known to spike blood sugar on camera, then shows you what his monitor did. The second is Jessie Inchauspé, a French biochemist known as the Glucose Goddess. She got interested while working at a genetics company that was testing these sensors, and wrote a bestseller called Glucose Revolution. Her best known advice comes down to four habits: a savory breakfast, a tablespoon of vinegar in a glass of water before you eat, eating your food in the right order, vegetables first, and moving after you eat.
Andrew Huberman, the Stanford neuroscientist behind Huberman Lab, one of the most popular health podcasts in the world, talks about glucose too. His rules: no food in the first hour after you wake up and none in the two to three hours before bed, a squeeze of lemon or a spoon of vinegar with your meal, and a walk after eating. His advice about not eating late shows up in the research too: in one study, the same dinner eaten at 10 pm spiked about 18 percent higher than at 6 pm. Peter Attia, the longevity doctor who wrote Outlive, wears a sensor to see how his own body responds, and argues it catches what a standard blood test can miss. His own line peaks at about 102 mg/dL.
In the United States, companies started selling these sensors through subscription apps aimed at the longevity crowd, usually 200 to 400 dollars a month. I paid about 50 dollars per sensor on Marketplace, for the same Dexcom sensor that most insurance covers for people with diabetes, and it comes with its own free app. Glucose went from a diabetes word to a wellness word.
Some of what these people say holds up very well, and some of it does not. A rise after a meal is not a disease. It is your body doing its job. The question is how high, how often and for how long. So first, what a spike actually is.
What a spike does.
When you eat bread, rice, fruit or sugar, your gut breaks it down into glucose and sends it into your blood. Your pancreas answers with insulin, the hormone that moves glucose out of the blood and into your muscles, your liver and your fat. In a healthy person that keeps blood sugar between about 70 and 140 mg/dL most of the day. A spike is the climb after a meal. What matters is how high it goes, how long it stays there and how hard it falls. Scientists rank foods by how fast they raise blood sugar, on a scale called the glycemic index. White bread, white rice and potatoes sit high. Lentils, nuts and most fruit sit low.
Insulin is also the brake on fat burning. It does not take much. A small rise in insulin is enough to cut the release of fat from your fat cells by half, and after a meal that brake stays on for a few hours. While insulin is up, your body burns the sugar you just ate and leaves your stored fat alone. So every time you spike, fat burning drops sharply until the sugar is used up. Your body turns surprisingly little sugar directly into fat, unless you eat more than you burn.
The exception is fructose. Table sugar is half glucose and half fructose. Glucose feeds your whole body. Fructose is handled mostly by your liver. A piece of fruit carries a little of it, wrapped in fiber and water. A soda delivers a flood with nothing to slow it down. In a ten week study at the University of California, people who got a quarter of their daily calories from fructose drinks, far more than you get from fruit, built more fat in their liver and around their organs. That is visceral fat, the dangerous kind. People who drank the same amount of glucose did not. Fructose is also the sugar that raises uric acid, which causes gout. Added sugar is the first thing I would cut. It is one of the best health moves you can make, and one of the hardest. The industry does not make it easier.
Think about the breakfast most of us grew up on. A bowl of cereal, pancakes with syrup, toast with jam, a glass of orange juice. That is a large dose of fast sugar on an empty stomach, and your blood sugar shoots up. Insulin comes in hard, and two or three hours later your blood sugar drops, often below where it started. In a study of more than a thousand people wearing these sensors, the people with the biggest drop felt hungrier, ate their next meal sooner, and ate about 312 calories more over the day. The dip after the spike is often what sends you looking for a snack at ten in the morning.
And the rush? When researchers pooled 31 studies of sugar and other carbs, the energy boost never showed up. Within an hour, people who had sugar felt more tired and less alert than people who had a placebo. By contrast, I train fasted, usually a heavy high intensity interval session 16 hours into my fast, with full energy.
The craving loop. What sugar does do is teach your brain to want more. Your gut can tell real sugar from an artificial sweetener, and it reports to your brain. In a German study, people who ate a sweet, fatty pudding every day for eight weeks ended up with a reward system, the dopamine circuit, that responded more strongly to that kind of food. It is a cheap hit, and the brain learns it fast. I notice it in my own body: after a day heavy in carbs and sugar, I crave more for the rest of that day and the next. What dopamine does to your choices, far beyond sugar, gets its own Experiment.
Swapping sugar for artificial sweeteners is not free either. In Experiment 005, Trust Your Gut, I wrote about a study of 120 people where two common sweeteners, saccharin and sucralose, changed how their bodies handled sugar within two weeks.
Even healthy people can spike hard. At Stanford, researchers gave healthy volunteers a bowl of cornflakes with milk, and 80 percent of them went past 140. One spike does not hurt you. Big spikes, again and again, can be a sign your body is losing its grip on sugar.
Sleep matters too. In one small study, a single night of four hours' sleep made healthy people respond to insulin about 20 percent worse the next day.
The road to diabetes.
Type 2 diabetes does not start with high blood sugar. It starts with cells that stop listening to insulin.
Here is how it goes. Your muscles and liver start answering insulin more slowly. Your pancreas makes up for it by making more. For years that works: your blood sugar tests come back normal because your pancreas is working overtime to keep them normal. Then one day it cannot keep up, and the sugar starts to stay in the blood. First that is prediabetes: an HbA1c, the test that shows your average blood sugar over about three months, between 5.7 and 6.4 percent. At 6.5 percent it is type 2 diabetes.
A British study followed thousands of civil servants for years before some of them were diagnosed. Their blood sugar crept up slowly for a long time, then climbed steeply in the last three years or so. By the time the number moves, the problem is years old.
My grandmother got diabetes late in life, after she moved full time to the village. She lived alone in a house with a garden full of fruit trees, eating a lot of that fruit. Her doctor blamed the fruit and told her to stop eating grapes.
It is not rare. In the United States, about 115 million adults have prediabetes, more than two in five, and eight in ten of them do not know it. In Canada, three in ten people have diabetes or prediabetes. Around the world, 589 million adults have diabetes. It is the leading cause of kidney failure, of lower leg amputations and of blindness in adults in the United States. Each daily serving of a sugary drink is linked to about a 13 to 18 percent higher risk of type 2 diabetes.
The good news is that it can go backward. In a British trial called DiRECT, almost half the people with type 2 diabetes who went through a weight loss program were in remission a year later, with normal blood sugar and no diabetes medication. The more weight they kept off, the better their odds.
Why mine stayed flat.
My guess is the fasting and what I eat.
I eat what I call hybrid keto: high protein, eggs, meat, lots of nuts, cheese, vegetables and olive oil, with no bread, pasta or rice, except the occasional croissant or pastry cheat. I do not believe in a hundred percent keto. It cuts out foods full of nutrients, like most fruit, beans and many vegetables, foods a lot of people enjoy that are actually good for you. All the restrictions make it very hard to keep up in a normal life, and a diet that is hard to maintain is not a good diet. Even Mark Sisson, who wrote The Keto Reset Diet and founded Primal Kitchen, the brand of keto friendly sauces and dressings, now talks about a more flexible version.
After about 12 hours without food, depending on how much sugar your liver has stored and how much you move, your body starts shifting from burning sugar to burning fat. When your body runs low on stored sugar, your liver starts turning fat into ketones, a fuel your brain and muscles can run on, and research suggests a more efficient one than sugar. That state is called ketosis. Ketones start rising around then. I fast 18 hours every day and eat low sugar, so every day I spend hours past that point. The longer the fast, the more of your day your body spends burning fat for energy. Fasting gets its own Experiment, including my longest fast so far, 75 hours.
Refeeding is as important as the fast itself. I usually break my fast with a glass of water and apple cider vinegar, then eggs and cheese, chickpeas or beans, kefir or kimchi, and lots of olive oil. The mix changes, but it is always high in protein, with vegetables and fat first. There is always a bowl of boiled eggs in my fridge. When I travel and stay somewhere with a kitchen, the first thing I buy is a dozen eggs to boil and some cheese. On flights where I will break my fast in the air, I sometimes carry a few boiled eggs, a piece of cheese, nuts and dried fruit, because we all know how bad plane food is. That is how I eat, and it lines up with all three habits in the last part of this piece.
I eat dates almost every day. I love them, and luckily they are good for you: fiber, potassium and a low glycemic index. When researchers tested five varieties of dates, all of them came out low, in healthy people and in people with diabetes.
And the drinking? While your liver is busy clearing alcohol, it slows down the sugar it releases into your blood, which can push blood sugar down, sometimes too low. I saw it on my own monitor. I drank a lot on New Year's Eve, and the next morning it kept sending me low alerts until noon. That drop is not a trick for better blood sugar. Alcohol is classified as a carcinogen, and it has plenty of other problems. It gets its own piece. With my busy social life, I have still brought my drinking down to a glass or two of wine a month, sometimes less. For someone who used to own clubs and restaurants, that is a big change.
Two things to know. First, if you eat low carb for days and then have a big plate of pasta, you can spike harder than someone who eats pasta every day, because your body has turned down its sugar handling for a while. It returns to normal within days of eating carbs again. Second, my results are mine. The same food can spike one person and not another. At the Weizmann Institute, one woman spiked on tomatoes. At King's College London, researchers gave twins the same meal and saw very different spikes, in people with almost the same genes. That is exactly why I wanted to test food on myself. My line is my line, not necessarily yours, but the general rules apply to everyone.
How we got here.
Sugar was not always cheap. In 1704 the average person in Britain ate about four pounds of it a year. By 1900 it was about ninety. That growth was built on plantations worked by enslaved people. Today the average American eats about 17 teaspoons of added sugar a day. The irony is not lost on me: I live in a loft in what used to be a sugar refinery.
The cereal breakfast is newer than it feels. The Kellogg brothers developed their flaked cereals in the 1890s, and the idea that breakfast is the most important meal of the day was pushed hard by cereal companies in the decades that followed.
In 1965, an industry group called the Sugar Research Foundation paid three Harvard scientists to write a review of what causes heart disease. It came out in 1967 in one of the most respected medical journals in the world, and it pointed at fat and played down sugar. It helped start fifty years in which fat was the enemy and sugar mostly got a pass. When the United States drew its first food pyramid in 1992, bread, cereal, rice and pasta sat at the base, six to eleven servings a day.
In January 2026, under Health Secretary Robert F. Kennedy Jr., the United States put out new dietary guidelines with the pyramid turned upside down, and for the first time they said no amount of added sugar is recommended.
Built to want more.
Your body has a signal that tells you when you have had enough. A lot of modern food is designed to get past it.
Food companies test combinations of sugar, fat and salt to find the exact point where you crave the most, and they have a name for it: the bliss point. When researchers at the University of Kansas looked at almost 8,000 foods in the official US food database, 62 percent met their definition of hyperpalatable: combinations of sugar, fat and salt that make food hard to stop eating. Food brands that tobacco companies owned in the 1980s and 1990s, when Philip Morris owned Kraft and RJ Reynolds owned Nabisco, were even more likely to be built that way.
Look at what hides in plain sight. A can of Coke holds about 39 grams of sugar, nearly ten teaspoons. Ketchup is about a quarter sugar, with a good dose of salt. Nutella's ads talked about hazelnuts and skim milk, but the first two ingredients on the label are sugar and palm oil, and more than half the jar is sugar. In 2012 its maker paid 3 million dollars to settle a lawsuit over calling it part of a balanced breakfast.
Calories still count. What changes is how many of them you eat. At the US National Institutes of Health, 20 people lived in a clinic for a month and ate two diets, two weeks each, matched for sugar, fat, fiber and salt. On the ultraprocessed diet they ate about 500 calories a day more, without trying, and gained weight. On the whole food diet they lost it. The math is real. The food decides how much of it you do.
The three levers.
Out of everything I read, three habits have the strongest research behind them for a flatter line. Three of the Glucose Goddess's four are on this list, and they are the three with the most studies.
Vinegar before you eat. One tablespoon of vinegar in a glass of water before a meal lowers the rise afterward. Across many trials the effect is modest, not magic, but it is real. Lemon juice works too: in one small study, people ate about two slices of white bread with lemon juice instead of water, and their peak came out 30 percent lower and about half an hour later. I take apple cider vinegar every morning with my first glass of water, and before meals whenever I can. I even travel with a small bottle. My go-to is apple cider vinegar with the mother, the cloudy layer of live bacteria, which I wrote about in Experiment 006, Well Preserved. Always dilute it. Vinegar is known to soften tooth enamel, so if you take it daily, using a straw helps, and do not brush your teeth right after.
Vegetables and protein first, starch last. Same plate, different order. In a study at Weill Cornell in New York, in people with type 2 diabetes, eating vegetables and protein first and the bread last cut the blood sugar rise by 37 percent at the one hour mark. Eating the carbs last also raises GLP-1, a hormone your gut makes that slows your stomach and tells your brain you are full. Ozempic is a peptide that mimics GLP-1, and peptides are what everyone is talking about right now. They get their own Experiment.
You see this habit in old cultures. The Romans started a meal with eggs and lettuce, and their saying for start to finish was "from the egg to the apples." A Lebanese table starts with mezze, plates of vegetables, olives and dips, long before the grilled meat arrives. The French open with crudités, raw vegetables. If you do one thing, start with the salad and veggies.
A few more tricks work the same way. Fat slows the spike. Better to skip the bread basket, but if you do eat it, butter, olive oil and balsamic vinegar help. And rice or potatoes that are cooked, cooled in the fridge and reheated end up with more resistant starch, a kind of starch your body digests slowly. That one gets its own piece.
Move after you eat. The Chinese have a saying for it: walk a hundred steps after a meal and you will live to ninety nine. Your muscles take in most of the sugar from a meal, and when they work, they pull glucose out of the blood without needing insulin at all. In a study in New Zealand, in people with type 2 diabetes, a ten minute walk after each meal lowered blood sugar more than one thirty minute walk a day. The biggest gain came after dinner. Even two to five minutes beats sitting. The benefits of walking get their own Lab Note.
Another hack: if you cannot get up, trick your body into thinking you are moving. Sit on the couch and do calf raises: heels up, heels down, again and again. For sugar, the muscle that matters is the soleus, deep in the calf. The calf is sometimes called your second heart, because it pumps blood back up from your legs. The soleus is built to work for hours without tiring. A small study at the University of Houston found this movement lowered the rise from a sugary drink by about half. That study ran for hours. A few minutes is likely to help. A working muscle is a sugar sponge.
The sweet spot.
Here is what I do. I fast 18 hours every day. Before I eat, a glass of water with apple cider vinegar. Then eggs and vegetables usually come first, with olive oil.
Here is what you can do tonight. Have a tablespoon of vinegar in a glass of water before you sit down. Start with the salad, and eat the bread or the rice last, or better yet skip it. Then take a ten minute walk.
A rise after a meal is normal. Living on a roller coaster of spikes and crashes is not. Scientists have a name for what you want instead: metabolic flexibility. It is your body's ability to switch fuels. When you eat carbs, it burns them and stores the rest. When the food stops, it moves smoothly to burning fat. A flexible body does not crash between meals or need a snack every three hours. Fasting and moving help train that switch. Living on sugar all day can wear it down. I will go much deeper into it in the fasting Experiment.
The goal is not a flat line. The goal is the sweet spot: a body that handles sugar well when you have it, and burns fat when you do not.
Experiment 008 is complete. You just read it.
Georges
Usually one Experiment on Sunday. Lab Notes in between. Free.