Weight Loss

Overview

Weight loss is a question of metabolic rate, not willpower or calorie restriction. Fasting, low-carbohydrate or ketogenic diets, and aerobic cardio all suppress thyroid function, raise cortisol, and burn through muscle and immune tissue rather than fat. On an extreme low-calorie diet, eighty percent of the weight a person loses is protein and water, with hardly a dent in the fat. The way to lose fat is to keep the metabolic engine running at full speed with enough sugar to keep the liver converting T4 to active T3, enough protein (mostly from milk and gelatin) to spare muscle, calcium and salt to stimulate metabolic rate, saturated fat to oppose stored polyunsaturated fats, strength-bearing exercise rather than aerobic cardio, and removal of the polyunsaturated oils that interfere with thyroid at every level.

Key Points

• Extreme calorie restriction and fasting destroy muscle, not fat. When the body senses starvation, it lowers T3 to slow tissue burning and shifts to breaking down protein for glucose. On a 10 to 14 day water fast, around 80 percent of the weight lost is protein and water, with hardly a dent in fat. The thymus dissolves within a few hours, the skin atrophies, and the calf and bicep muscles shrink toward the size of a finger. Each cycle of dieting makes the next round of weight gain easier because shrinking muscle means lower resting calorie burn, so chronic dieters can gain weight on 700 to 800 calories a day.

• Moderate calorie reduction with adequate nutrition flips the ratio. A 500 to 800 calorie diet that includes enough minerals (sodium, calcium, magnesium, potassium) and protein to suppress the stress response can produce 80 percent fat loss and only 15 to 20 percent protein loss. The minerals matter as much as the calories. Without them, cortisol rises and the body cannibalises muscle even with food in the diet, so the right strategy is fewer calories of the right composition rather than fewer calories of anything. This point is not made to suggest a 500 to 800 calorie diet - it's intended to show that nutrition affects what gets burnt.

• Body recomposition matters far more than scale weight. A pear-shaped person who diets and exercises often becomes a smaller pear, with the same unhealthy fat distribution. The Biggest Loser contestants lost most of their weight as lean muscle, dropped basal metabolic rate by 40 to 50 percent, and every winner regained the weight on fewer calories than before. The ratio of lean muscle mass to fat mass is the primary determinant of basal metabolic rate, so losing muscle alongside fat tanks metabolism long term.

• Sugar feeds the liver to keep thyroid active. The liver converts 60 to 70 percent of T4 into active T3, and it requires glucose to do it. On a high-protein, low-carbohydrate, or ketogenic diet, T3 falls close to zero within hours of using up stored glycogen, and the body switches to cortisol-driven protein breakdown. Sucrose (50% fructose and 50% glucose), fructose, and lactose specifically support T3 production, and animals that had Coca-Cola added to their diet became lean and could eat more without gaining weight, because fructose preferentially raises glycogen stores rather than triggering insulin and fat synthesis.

• Milk and gelatin are the best proteins for fat loss. Milk's calcium inhibits fatty acid synthase (the fat-forming enzyme that goes wild in cancer) and activates the uncoupling proteins that burn calories faster while protecting the mitochondria from oxidative damage. Gelatin lacks the inflammatory growth amino acids tryptophan, cysteine, and methionine, which suppress thyroid in adults. A military study found about 100 grams of protein a day is the minimum for work efficiency, and muscle meat, fish, and chicken should be limited to small portions because their excess tryptophan and cysteine drives stress and inflammation.

• The NCA stack for fat loss. Niacinamide at 50 to 100 mg three times daily (capped at 300 mg total) inhibits excess lipolysis without blocking baseline, raises NAD+, and produced 47 percent reduction in visceral fat mass in one animal study. A single 100 mg dose dropped triglycerides by 75 percent in fasted humans. Aspirin in higher doses uncouples metabolism similarly to the banned weight-loss drug dinitrophenol, and in lower doses inhibits cortisol synthesis (via 11-beta-HSD1) and aromatase. Caffeine at just 50 mg raises basal metabolic rate by 6 percent for over 12 hours and synergizes with aspirin to prolong both compounds' effects.

• Polyunsaturated fat is the main thing blocking fat loss. PUFA interferes with thyroid at every level: secretion from the gland, transport in the blood, conversion in the liver, and binding inside the cell. Cells preferentially burn saturated fats and store polyunsaturated fats. As time goes on, the stored fat becomes increasingly polyunsaturated and each round of fat mobilisation is more anti-thyroid and more pro-estrogenic than the last. Animals on a low-fat, high-PUFA diet got just as fat as animals on a high-fat, high-PUFA diet, while animals on high saturated fat did not.

• The goal is to pee fat out, not burn it. The liver glucuronidates fatty acids, especially PUFAs, making them water-soluble for excretion. Foamy urine is a sign this is working. Around 40 percent of fat loss can happen this way, with no oxidative byproducts. Strenuous exercise stops the process because the liver gets diverted to handling endotoxin and stress byproducts. A high-sugar, low-stress lifestyle with weightlifting therefore eliminates fat more safely than cardio plus dieting.

• Coconut oil is thermogenic and helps clear stored PUFA over time. The short and medium chain saturated fats in coconut oil compete against polyunsaturated fats in the mitochondria, restoring oxidative metabolism while they are being digested. A tablespoon a day can sometimes produce a pound a week of weight loss. A teaspoon three times a day is the right dose for someone with a very low metabolic rate, with no more than a tablespoon at one time recommended, because heart rate, breathing, and skin pinkness rise noticeably for an hour after a single dose.

• Aerobic cardio damages metabolism. One hour of moderate treadmill walking, with the pulse only at 120, dropped subjects' T3 close to zero in published experiments. Long-distance runners have atrophied hearts, lungs, and brains alongside their atrophied muscles, with sport-related anemia and reduced testosterone, all under the cover of a low resting pulse that is treated as fitness.

• Concentric exercise is the right kind of exercise for fat loss. Concentric movement loads the muscle on contraction with no load on relaxation: bicep curls where you drop the weight, climbing stairs (and taking the elevator down), pushing heavy carts, rowing, biking, swimming, sprinting. This builds muscle and mitochondria without the damage of eccentric work. Concentric loading also turns muscles into local factories for testosterone in men and progesterone and DHEA in women, replacing what cortisol depletes. At rest, muscle burns predominantly fat, so more muscle means more passive fat oxidation.

• The stress hormones make fat loss structurally impossible. Cortisol breaks down protein, adrenaline cuts circulation to the extremities, estrogen wastes oxygen and pulls polyunsaturated fats out of storage, and serotonin from a stressed gut activates the whole cascade. Until the underlying stress is turned off through adequate sugar, salt, calcium, magnesium, sleep, and removal of polyunsaturated fat, no amount of restriction will produce real fat loss; the body will defend its fat and burn its muscle instead.

• Cortisol blockade produces fat loss without dieting. RU486 (mifepristone), originally developed by Sanofi as a cortisol blocker before being marketed as an abortion pill, produces sustained weight loss in obese patients without any change to diet or exercise. Anti-adrenaline drugs like clonidine do the same. Emodin, a quinone found in cascara bark, inhibits 11-beta-HSD1 (the cortisol-synthesizing enzyme) and is in human trials for diabetes. The mechanism is anti-stress, anti-lipolysis, anti-fatty-acid-oxidation, which is why fat gain is fundamentally an endocrine problem, not a calorie problem. This is not an endorsement of the aforementioned drugs.

Notable Quotes

"On an extremely low calorie diet, the weight loss was about 80% protein and only something like 15 or 20% fat. But if they took a moderate amount of nutrition, enough to reduce the stress hormones, they could lose 80% fat and only 15 or 20% protein tissue."

[Ray Peat — Listener Q&A]

"The way your body makes carbohydrate is by destroying protein."

[Ray Peat — All Things Hormones, Metabolism and Health (Win At Life Podcast)]

"If a person really wants to concentrate on losing weight, milk and gelatin are the most favorable for weight loss, partly because the milk comes with such a generous supply of calcium, and calcium powerfully stimulates the metabolic rate."

[Ray Peat — Sugar Part 2]

"I added a tablespoon (of coconut oil) per day and lost a pound a week and stabilized 12 pounds lower."

[Ray Peat — Thyroid and Polyunsaturated Fatty Acids]

"A low-fat, pure PUFA diet was as fattening, as a high-fat, high PUFA diet. But a high-fat, all-saturated fatty acid diet wasn't fattening."

[Ray Peat — Dr. Ray Peat, Day Two: Full Interview from On the Back of a Tiger]

"Niacinamide doesn't inhibit baseline lipolysis. It only inhibits the excess lipolysis, which is triggered by things like very high adrenaline and cortisol."

[Georgi Dinkov — #84: Serotonin Elevated in Depression | SHBG | Anti-Obesity Effects of Niacinamide | CBDCs in 2023?]

"If you carry extra weight, if your BMI is let's say 31, and you start running suddenly to actually lose this extra weight, you may get yourself to a situation where lipolysis is so elevated, you can actually shut down a pancreas and give yourself type 1 diabetes."

[Georgi Dinkov — Georgi Dinkov, Brad Marshall on Obesity Causes and Solutions (July 11, 2022)]

Important Things To Consider

Temperature and pulse measure metabolism better than the scale. Resting morning oral temperature should be around 98 degrees Fahrenheit, rising to 98.6 by midday. Resting pulse should be 75 to 85, not the falsely "healthy" 50 of the endurance athlete. Marathon runners with low pulses are showing suppressed metabolism, not fitness.

Initial weight on a good diet is muscle and water, not fat. Women coming out of restrictive diets typically lose 10 to 15 pounds of water in the first week as their tissue comes out of stress, then put on weight for about a month as muscles regrow. Waist, thighs, and hips shrink while the scale goes up because muscle is denser than fat. The right metric in this period is the tape measure, not the bathroom scale.

Polyunsaturated fat takes years to clear from stored body fat. Stored fat turns over slowly and each pass preferentially burns the saturated portion while leaving the polyunsaturated. Even on a perfect diet, someone who has been eating seed oils for decades may take three or four years to substantially shift their tissue saturation index. The fatter the person, the longer this takes.

Calcium powerfully stimulates metabolic rate. Beyond inhibiting fatty acid synthase and activating mitochondrial uncoupling proteins, calcium and salt potentiate thyroid action. Aim for roughly 1.5 to 2 grams of calcium a day from milk and cheese, with eggshell powder as a substitute if large volumes of milk are not tolerated.

Carrots and bowel function reduce estrogen recirculation. Estrogen is excreted in bile and reabsorbed if the bowel is sluggish. A daily raw carrot binds estrogen and bacterial endotoxin and carries them out, lowering estrogen-driven fat storage. Mushrooms work similarly. The intestine is one of the main sites where weight problems are decided.

A waterlogged hypothyroid person retains water rather than evaporating it. A healthy person with normal thyroid evaporates about one liter of water per 1000 calories burned. If you drink half a gallon of fluid and excrete most of it as urine, your metabolic rate is very low. Adequate evaporation is one of the cleanest signs that the metabolic engine is running.

A fast pulse with a low temperature means adrenaline, not metabolism. Hypothyroid people often wake with a high pulse driven by adrenaline before cortisol has caught up to slow it down. Trying to lose fat in this state will simply burn more muscle.

Aging and stress turn fat tissue into an estrogen factory. Any de-energised, irritated tissue, especially fat, becomes a source of aromatase and estrogen production. Polyunsaturation in the stored fat amplifies this, so an overweight or aging person produces estrogen from their fat which drives further fat storage. Reducing PUFA, supporting thyroid, and getting estrogen down through progesterone is the way to break the loop.

Do not overshoot lipolysis if carrying significant excess fat. Flooding the bloodstream with free fatty acids (mostly PUFA) damages organs. Acute kidney injury, acute pancreatitis (roughly 30 percent fatal), and heart attacks in diabetics are largely caused by circulating PUFA released under stress. Rapid forced fat loss can produce eye floaters, blood sugar spikes over 100, and lipofuscin spots on the skin from peroxidation byproducts.

Take vitamin E and eat saturated fats to balance PUFA released during fat loss. A spoonful of coconut oil a couple of times a day, plus mixed tocopherols vitamin E, prevents peroxidation of PUFA being released from fat stores. Vitamin E has a 48 to 60 hour half-life and accumulates in the liver, so 2 to 3 times a week is enough. 100-200mg is a reasonable dose of Vitamin E.

Below 15 percent body fat, dietary changes beyond avoiding PUFA are largely unnecessary. At low body fat percentages, baseline lipolysis combined with muscle's preference for burning fat at rest will handle fat loss relatively comfortably. Above that threshold, restricting dietary fat (especially PUFA) while keeping carbohydrate intake adequate makes more sense, since carbohydrates keep lipolysis controlled while stored fat slowly comes down.