Chapter 2: How Fat Loss Actually Works: Energy, Insulin and Hunger

Summary: Keto helps you lose fat the same way every diet does, by eating less energy than you burn, but cutting carbs tends to lower appetite so the deficit takes less willpower.

On this page

The short answer
Deficit vs restriction
What insulin does and does not explain
Why eating less gets easier
What the head-to-head trials found
What this means for your plan
When to involve your doctor
Related

The short answer

Fat loss needs an energy deficit. That rule does not change on keto.

What keto changes is how hard the deficit feels. Many people who cut carbs find they are less hungry and eat less without trying. Over months, that matters more than any special effect of ketosis.

The trials back the plain version of this story. Low-carb and ketogenic diets often lose a little more weight early, and the gap shrinks or disappears by one to two years. Which diet you can keep matters more than which diet you pick.

KetoDick on this: His position is that "calories in, calories out" is mostly true but beside the point. The real question, in his framing, is how to eat less without feeling terrible, and his answer is to control insulin by cutting carbs, so the diet "doesn't rely on willpower" (from the video) (video 9AGpKAfs3Yk).

Deficit vs restriction

Two terms get mixed up, and the difference is the heart of this chapter.

Term	What it means	Is it needed?
Calorie deficit	You take in less energy than you use, by any route	Yes, for fat loss
Calorie restriction	You force intake down to a set number, often while hungry	No, if appetite drops on its own

A deficit is the result. Restriction is one way to get there, and often the hardest way.

Metabolic-ward studies, where every bite is measured, show the energy ledger still governs fat loss on a ketogenic diet. In one, 17 men switched to a ketogenic diet at the same calories. Energy expenditure rose by about 57 kcal a day, and body-fat loss slowed after the switch (Hall 2016). A small bump in calories burned is not a shortcut around the deficit.

KetoDick on this: His line is "calorie deficit matters but calorie restriction is not advisable" (from the video). He tells beginners to count carbs and let appetite set the rest (video 8Jk5ShSUpFY; video LbPnm9T0oxc).

What insulin does and does not explain

Insulin is a hormone that rises after you eat, most of all after carbs. Physiology references describe ketone production in the liver as regulated by insulin and glucagon (StatPearls, Ketogenesis). Cut carbs, and insulin falls and ketone production rises.

The "carbohydrate-insulin model" goes one step further. It says lower insulin is what causes fat loss, so carb cuts should beat fat cuts at the same calories.

Ward data do not support that strong version. In a study of 19 adults at the same calories, body-fat loss was 53 g a day with carb restriction and 89 g a day with fat restriction (Hall 2015). In the year-long DIETFITS trial, how much insulin people secreted did not change which diet worked better for them (Gardner 2018).

So insulin is part of the story, mainly through appetite, but it is not a calorie-free pass.

KetoDick on this: He says high insulin blocks the body's access to stored fat, which is his answer to why a heavy person can still be hungry (video s_sNd1v8Low). The ward studies above did not find extra fat loss from lower insulin at equal calories. Both points are stated here so you can weigh them.

Why eating less gets easier

If keto has an edge, appetite is where it shows up. Many people report less hunger and fewer cravings once carbs are low.

Protein helps here too, on any diet. In one trial, raising protein from 15% to 30% of energy, with carbs held steady, led people to eat 441 fewer kcal a day on their own and lose 4.9 kg over 12 weeks (Weigle 2005). A review of 24 trials found energy-restricted high-protein diets gave modestly more weight and fat loss and less loss of fat-free mass (Wycherley 2012).

That is one reason the protein chapter treats protein as a target, not an afterthought.

KetoDick on this: In his own early logs he reports coming in 800 to 1,000 kcal under his allowance without wanting more food (video 9Hk0jRb_9Es). In 2019 he agreed with a Men's Health article that keto works by suppressing appetite: "that's the point" (from the video) (video 1JbK1_ClDmY).

What the head-to-head trials found

Randomized trials have compared low-carb or ketogenic diets with low-fat diets for decades. The pattern is consistent: an early lead for low-carb, then a small or no difference.

Trial	Who and how long	Result
Foster 2003	63 adults, 12 months	Low-carb lost more at 3 and 6 months; not significant at 12; many dropped out of both arms
Samaha 2003	132 adults with severe obesity, 6 months	Low-carb 5.8 kg vs low-fat 1.9 kg
DIRECT, Shai 2008	322 adults, 2 years	Low-fat 2.9 kg, Mediterranean 4.4 kg, low-carb 4.7 kg
DIETFITS, Gardner 2018	609 adults, 12 months	Healthy low-fat 5.3 kg vs healthy low-carb 6.0 kg; not significantly different
Bueno 2013	13 trials of 12 months or more	Very-low-carb ketogenic diets lost 0.91 kg more than low-fat

The National Lipid Association's review reached the same place: low- and very-low-carb diets are not superior for long-term weight loss and may give more short-term loss (Kirkpatrick 2019).

Two limits apply. DIETFITS used a moderate low-carb arm, not a ketogenic one. And most participants were adults with overweight or obesity, not specifically women aged 30 to 60.

What this means for your plan

Put the pieces together and a simple plan falls out.

Cut carbs first. This is the step that tends to lower appetite. See Keto Basics.
Hit your protein. It supports fullness and helps keep muscle while you lose fat. See protein and satiety.
Eat fat to fullness early, then let it fall. Fat fills the gap while you adapt. Later, fat is the dial that moves. See how much fat.
Track at least while you learn. A log shows whether a deficit is actually happening. See Starting Keto.
Judge by months, not days. Early drops are mostly water, and stalls are normal. See Plateaus and hidden calories.

If you feel you are white-knuckling hunger every day, treat that as a signal to adjust, not a test to pass.

KetoDick on this: He tells people in month one not to restrict calories at all: eat protein first, keep carbs low, and eat fat to fill hunger. Only past about week six, if still hungry, does he say to look for hidden sugars, triggers or psychological factors (video 7Aixw4uRksI).

When to involve your doctor

Cutting carbs can change blood sugar and blood pressure quickly. Talk to your doctor before you start, and especially about dosing, if any of these apply:

You take medication for diabetes. In one non-randomized program, people on a very-low-carb diet ended up using less diabetes medication (Hallberg 2018), which is why doses need a doctor watching.
You take blood pressure medication.
You have kidney disease.
You are pregnant.
You have a history of an eating disorder. Deliberate restriction can tip into harm.

See who should talk to a doctor, medications and eating disorders.

KetoDick on this: He tells anyone with a condition or on medication to review his advice with their doctor, especially dosing (video UygKGoP_BtA). He also warns that chasing posted results can tip into anorexia, and says to include a doctor in any restriction plan (video 7Aixw4uRksI).

In this chapter

Guide

Protein · How to read a study

Blog

Videos

Previous: Chapter 1: Keto Basics · Next: Chapter 3: Starting Keto

Last verified: 2026-10-31