What Is the Keto Diet and How Does It Work? Insulin, Ketones and Hunger Explained
In this video
My one-video answer to "what is keto?" It moves fast: what ketosis is, why I thought it works, then the protein and carb numbers.
- [0:00] Keto is one kind of low-carb diet. I said studies found low carb gets better adherence than low fat.
- [0:30] Cut glucose for long enough and glycogen in the liver and muscles runs down. The body speeds up fat breakdown and makes ketones: beta-hydroxybutyrate (BHB), acetoacetate and acetone.
- [1:00] Insulin gets in the way of lipase, the enzyme that breaks down stored fat. Chronically high insulin is where I placed insulin resistance, pre-diabetes and type 2.
- [2:00] Fat adaptation takes two to four weeks in thinner people and three to eight in heavier people.
- [2:30] Calories in, calories out is "still true and … irrelevant" (from the video). The real question is how to eat less and stay comfortable.
- [3:00] Unlocking fat stores is my answer to "why are heavy people still hungry?"
- [3:30] People who counted only carbs got results not significantly different from people who counted carbs and calories.
- [5:00] A ketogenic diet "is not food specific" (from the video). Any mix that keeps you in ketosis counts.
- [5:30] No grain, no dairy, grass-fed only: optional extras. People also use keto for epilepsy and some tumours.
- [7:00] Adequate protein: women from about 50–60 g up to 100–120 g; men from about 80 g up to 140 g or more for intense athletes. Carbs under 20 g to start, some tolerate up to 50.
- [8:00] Hydration, electrolytes, fibre and leafy greens matter, even though greens carry carbs.
Watching this in 2026
This is the video I'd point a friend to first. The chain is easy to follow: carbs down, insulin down, fat available, hunger down, so you eat less without forcing it. Every other explainer on the channel is a variation on it, and the adherence video is the same "secret" told again (video 9AGpKAfs3Yk).
I'd cut some of the vocabulary now. Naming three ketone bodies and an enzyme in the first minute is a lot for someone who just wants to know what to eat. The answer to that comes at [5:00], and it's the most useful line in the video: keto isn't a list of foods, it's a carb limit.
The claim worth unpacking: is the "secret" a metabolic advantage?
There are two claims tangled together here, and the evidence treats them differently.
The hormone part. Insulin does regulate ketone production. Ketogenesis in the liver produces acetoacetate, BHB and acetone, and it's regulated by insulin and glucagon (StatPearls, Dhillon & Gupta). Cutting carbs to lower insulin and switch on ketosis is textbook.
The fat-loss part. Later in the video I said low carb keeps your metabolic rate up and avoids the slowdown of low-fat diets. Metabolic-ward studies, where researchers control every bite, tested something close:
- In Hall et al., 2015, 19 adults lost 53 ± 6 g of body fat a day when carbohydrate was cut, against 89 ± 6 g a day when fat was cut.
- In Hall et al., 2016, 17 men switched to a ketogenic diet at the same calories. Energy expenditure rose 57 kcal a day, but body-fat loss slowed after the switch.
So at equal calories, keto didn't burn more fat. That's where my explanation and the literature differ. Where they agree is my own [2:30] line: calories still count. If keto works for you, the likeliest reason is the one I gave next, that you ate less without being hungry. The ward studies don't test that part, because they fix intake. More in Kevin Hall's metabolic-ward studies.
The adherence part. I opened with "low carb has better adherence than low fat." The named trials are more mixed. In Foster et al., 2003, retention was low in both arms. In DIETFITS, 12-month weight loss didn't differ significantly between healthy low-carb and healthy low-fat. Adherence is personal. That fits the line I'd keep: pick the version you can actually stay with.
The line that didn't hold up
At [0:30] I said the brain runs mostly on acetoacetate and acetone, and the muscles on BHB (video s_sNd1v8Low). The classic fasting study found that after weeks without food, BHB and acetoacetate replaced glucose as the brain's main fuel (Owen et al., 1967). BHB belongs on the brain's list, and acetone doesn't lead it. It changes nothing about what you eat, but it's a detail I got wrong.
Checking the protein numbers
My ranges were meant as "adequate," not a target. For comparison, the US adult RDA is 0.80 g per kg of body weight a day (IOM, 2005). For a woman weighing 70 kg (about 154 lb), that's 56 g. My 50–60 g starting point sits right at the RDA. My 100–120 g upper end is closer to the 1.2–1.6 g/kg a day that one review linked with better appetite control and weight management (Leidy et al., 2015). Both views are in is the protein RDA enough? and how much protein.
Who should start this with their doctor
If you have type 2 diabetes or pre-diabetes, the mechanism I described is exactly why your doctor needs to know. Cutting total carbohydrate has the most evidence for improving blood sugar (American Diabetes Association, Evert et al., 2019), so medication doses may need to change. The same goes for anyone thinking of keto for epilepsy or cancer: that's a plan for your specialist.
Key points
- Keto is a low-carb diet strict enough to make the liver produce ketones. Insulin and glucagon regulate that switch.
- The food rule is a carb limit. Grain-free, dairy-free and grass-fed are optional extras.
- At equal calories, metabolic-ward studies found no extra fat loss on keto (Hall 2015, Hall 2016).
- The practical case is appetite: less hunger, so less food, without counting calories.
- After weeks of fasting, the brain runs on BHB and acetoacetate (Owen 1967).
- Diabetes medication: talk to your doctor before cutting carbs.
Related
- Guide: keto basics · ketosis · fat adaptation · types of keto · insulin · energy balance
- Blog: does insulin make you fat? · the metabolic advantage · does ketosis mean burning fat? · why am I not hungry?
- Videos: keto's advantage is adherence · do calories still matter? · banned foods and dose · eating too much fat