Cold hands and feet, an afternoon slump that arrives at the same time every day, and the feeling that your body is running on low power. If you want to speed up your metabolism, what you mostly find online are lists of ginger, green tea, chilli and intermittent fasting.
The biologist Ray Peat approached the topic from a different angle over several decades. For him, the metabolic rate was the most important indicator of how well the body is supplied with energy. Here you will learn how Peat understood metabolism, how you can observe it yourself with a thermometer and your pulse, and which foods play a role in his approach to stimulating metabolism.
Who was Ray Peat?
Raymond Peat (1936 to 2022) earned his doctorate in biology at the University of Oregon and focused above all on hormones, in particular progesterone and the thyroid hormones. In his newsletters and articles he combined physiology, biochemistry and nutrition into an overall picture of his own, which today is often called the pro-metabolic diet.
Some of his approach is based on well-documented physiology, some on animal studies, older literature or his own interpretation. That is why we present his view here as a way of thinking and point out where its limits lie.
You can find an overview of his philosophy in the article Hormones and nutrition: Ray Peat’s pro-metabolic philosophy.
What metabolism meant to Ray Peat
By metabolism, Peat mainly meant the ability of cells to produce energy from food and oxygen. This process takes place in the mitochondria, and part of the energy produced is released as heat. A well-functioning metabolism therefore shows itself very directly in body warmth.
For Peat, the most important lever is T3, the active form of thyroid hormone. T3 increases oxygen consumption and heat production in almost all cells. For the thyroid and the cells to work well, the body needs enough energy from food, especially carbohydrates and protein.
Peat saw the stress hormones as the opposing force, above all cortisol and adrenaline. They keep blood sugar up when too little energy comes in, for example during long fasts, with very few carbohydrates or under ongoing stress. In the short term this is a useful protective mechanism. If it becomes a permanent state, in Peat’s view the body turns down heat production and switches into saving mode.
We describe in more detail how nutrition influences energy production in the cells in the article on mitochondria and vital energy.
Slow metabolism: typical signs
Here Peat drew on the work of the American physician Broda Barnes, who as early as the 1940s used body temperature as an indicator of thyroid activity. These signals come up again and again in Peat’s writing:
| Signal | Explanation from Peat’s point of view |
|---|---|
| Cold hands and feet | The body keeps the warmth in the trunk and saves on hands and feet |
| Low body temperature | The cells produce little heat overall |
| Low pulse without athletic training | The heart is working in saving mode |
| Energy slump and cravings in the evening | Stress hormones keep blood sugar up |
| Slow digestion | With less energy, the gut also works more slowly |
These signals are unspecific and can have many causes, from iron deficiency and lack of sleep to a thyroid disorder. If they persist over a longer period, they should be checked by a doctor.
Why your hands often get cold first is explained in the article Why are your hands always cold?
Testing your metabolism: measuring temperature and pulse
Peat’s most practical suggestion only needs a thermometer and a watch. Measure your body temperature and resting pulse at several points during the day.
In the morning straight after waking up, while still in bed. This is the baseline after the night.
After breakfast, about 20 to 30 minutes after eating. With an active metabolism, temperature and pulse rise after the meal.
In the afternoon, when the body is normally at its warmest.
As a guide, Peat named a temperature of around 37 degrees Celsius over the course of the day and a resting pulse of about 85 beats per minute. He found the pattern across the day particularly revealing. If the temperature drops after breakfast, in his view this suggests that stress hormones had been keeping the temperature up beforehand.
Be careful with the pulse: people with endurance training often have a low resting pulse without their metabolism being slow. The measurements do not replace a blood test either. But they help you observe over a few weeks how your body responds to changes in diet, sleep and stress.
Why Ray Peat avoided PUFA
PUFA stands for polyunsaturated fatty acids. They are found in large amounts in sunflower, safflower, soybean and canola oil, in margarine and in many processed foods.
Peat saw them as one of the most important brakes on metabolism. Polyunsaturated fatty acids oxidise easily, they are stored in fat tissue and released again during stress or fasting, and in his opinion they impair the action of thyroid hormones and energy production in the mitochondria.
This view is controversial in nutrition science. Official professional bodies continue to recommend vegetable oils as part of a balanced diet. If you want to follow Peat’s approach, you cook mainly with butter, ghee, coconut fat or beef tallow and avoid highly processed cooking oils.
You can find the arguments in detail in The science behind Ray Peat’s criticism of unsaturated fatty acids and in the article on omega-6 overload.
Sugar and carbohydrates as fuel
Perhaps the most unusual part of Peat’s approach: he saw sugar from fruit, fruit juice, honey and milk as a valuable source of energy. His reasoning was that the body has to release fewer stress hormones to maintain blood sugar when enough glucose and fructose are available.
Typical of Peat’s diet are therefore freshly squeezed orange juice, ripe fruit, milk and honey, spread across regular meals. He was critical of long fasting periods and very low-carbohydrate diets because, in his view, they raise cortisol levels. You can read how cortisol and evening hunger are connected in Hunger in the evening: what cortisol has to do with it.
For many people, a spoonful of honey in warm milk is the easiest way to start, for example with our honey with wild blueberries. If you have blood sugar problems or diabetes, you should discuss changes to your carbohydrate intake with your doctor first.
Why fruit, milk and honey form the foundation is explained in Fruit, milk and honey: the cornerstones of the Ray Peat diet.
Protein, gelatine and liver
For Peat, enough protein was a prerequisite for the liver and thyroid to work well. He preferred dairy products, eggs, cheese, shellfish and meat from ruminants.
Gelatine played a special role here. Muscle meat contains a lot of tryptophan and methionine, whereas gelatine contains a lot of glycine and proline. Peat recommended complementing muscle meat with gelatine or bone broth to make the amino acid profile more balanced, as was taken for granted in the past when the whole animal was eaten. You can put this into practice with a classic broth or with our bone broth powder from organic grass-fed beef and the collagen hydrolysate powder.
Peat counted liver among the most valuable foods of all because of its vitamin A, copper and B vitamins. He advised about one portion per week. Beef liver is one of the richest natural sources of vitamin B12, and for vitamin B12 the claim is authorised that it contributes to normal energy-yielding metabolism. Because of the high vitamin A content, regular small amounts are best. During pregnancy, you should only eat liver after consulting your doctor.
If you avoid the taste, you can also find liver freeze-dried, for example in our organic beef liver capsules from Estonian pasture farming. It remains a food and replaces neither a balanced diet nor medical treatment.
How to build liver capsules sensibly into your everyday life is explained in Beef liver capsules experiences: how to get the most out of them.
Salt, milk and carrot salad
Peat added a few details to his diet that seem unusual at first glance. He saw salt as a help in relieving the body under stress and advised against restricting it heavily without a medical reason. He valued milk and cheese as a source of calcium because a good ratio of calcium to phosphorus was important to him. He also recommended a raw carrot salad with a little vinegar, coconut oil and salt, which in his view reduces the burden on the gut from bacterial substances.
On top of that come factors beyond the plate: enough sleep, daylight, warmth and as little ongoing stress as possible. You can read more about salt in Salt: we learned it differently.
What speeding up your metabolism realistically means
No single food and no home remedy kick-starts your metabolism at the push of a button. Peat’s approach aims to release the brakes: eating enough, regular carbohydrates and protein, few polyunsaturated fats and less ongoing stress. How strong the effect is varies from person to person, and many of his theses lack large clinical studies.
With a thermometer and pulse measurements you can observe this in yourself. If you have persistent tiredness, sensitivity to cold or unexplained weight changes, having your thyroid checked by a doctor is still the right first step.
How the principles can be put into practice is shown in From theory to practice: Ray Peat principles in everyday life.
Frequently asked questions
What did Ray Peat say about metabolism? Peat saw the metabolic rate as a central indicator of health. In his view, an active metabolism shows itself in warm hands and feet, stable energy and a body temperature of around 37 degrees. As the most important brakes, he named stress hormones, polyunsaturated fatty acids and too little food.
How can I test my metabolism? Measure your body temperature and resting pulse in the morning in bed, after breakfast and in the afternoon. Peat paid particular attention to whether the values rise after eating. A blood test is needed to have your thyroid checked.
Which foods stimulate metabolism? According to Peat, mainly easily digestible carbohydrates such as fruit, fruit juice and honey, along with dairy products, eggs, gelatine and a little liver on a regular basis. For him, the decisive factor was the overall diet with regular meals.
Why did Ray Peat recommend sugar? In his view, with enough sugar intake the body needs less cortisol and adrenaline to stabilise blood sugar. He meant sugar from fruit, juices, honey and milk, as part of a protein-rich diet.
What are PUFA? PUFA are polyunsaturated fatty acids, found above all in seed and vegetable oils. Peat considered them a burden on metabolism. This view is debated controversially in nutrition science.
Does fasting help speed up metabolism? From Peat’s point of view, rather not. Long fasting periods raise stress hormones, and the body responds by saving energy. He recommended regular meals with carbohydrates and protein.
Which home remedies stimulate metabolism? In Peat’s sense, they are simple habits: breakfast shortly after getting up, orange juice with a pinch of salt, warm milk with honey, daylight and enough sleep. Their effect comes from regularity over weeks.