How to Eat

The pattern everyone agrees on

• Mostly plants, mostly whole. At least 400 g (five portions) of vegetables and fruit a day, not counting potatoes.¹ Whole grains rather than refined. Legumes, nuts and seeds most days.
• Fiber: 25 to 30 g a day. The single most under-appreciated recommendation in nutrition. People eating that much have roughly 15 to 30 percent lower rates of heart disease, stroke, type 2 diabetes and colorectal cancer than people eating the least.² Most adults in rich countries manage about half.
• Protein: 1.2 to 1.6 g per kilogram of body weight a day, spread across meals rather than piled into dinner. For a 70 kg adult that is 85 to 110 g. Over sixty, do not drop below 1.0 to 1.2 g/kg: older muscle responds less to each meal, so it needs more.³
• Fat: unsaturated over saturated. Olive and other plant oils, nuts, oily fish, in place of butter, lard and fatty meat, with saturated fat under 10 percent of energy.¹ Replacing saturated with unsaturated fat lowers LDL cholesterol and heart disease risk. Seed oils are not poison; the donut is the problem, not the canola in it.
• Free sugars: under 10 percent of energy, ideally under 5. Roughly 50 g a day at most, 25 g for the better target; a can of cola is about 35 g.¹ The 2026 US guidelines go further and set no recommended amount at all.⁴
• Salt: under 5 g a day (about a teaspoon, 2 g sodium). Most of it arrives in bread, sauces and packaged food, not from the shaker.¹
• Ultra-processed food: as little as you can manage. In the one tightly controlled trial, people given an ultra-processed diet ate about 500 calories a day more than the same people on a matched unprocessed diet, without noticing, and gained weight in two weeks.⁵
• Alcohol: less is better. No amount is protective; the “glass of red wine” finding did not survive better studies.⁶
• Water: when you are thirsty, and with meals. Eight glasses is not a rule; pale-yellow urine is the gauge.

The plate, so you never have to count

Then the three checks from Volume 1, in the shop and at the end of the day:

1. Turn the package over. If the ingredient list contains things you would not find in a home kitchen (emulsifiers, gums, isolates, anything with a number instead of a name), it is ultra-processed, whatever the front says.
2. Apply the shelf-life check. If it can sit on a shelf for longer than the average mammalian pregnancy without spoiling, ask what is keeping it that way, and treat that as your answer.
3. Count today’s fiber sources, not grams. Vegetables, fruit, whole grains, legumes, nuts, seeds actually eaten today. Fewer than three and your 38 trillion gut microbes noticed before you did.

The arithmetic

Body weight follows energy balance: calories in against calories out, over weeks, not days. The rest is detail, and the detail is where people get lost.

1. What out is. Most of what you burn is just being alive: roughly 1,400 to 1,900 calories a day for most adults before you move at all, more if you are bigger or carry more muscle. Deliberate exercise adds a modest slice on top, which is why exercise is a poor weight-loss tool and an excellent everything-else tool.
2. What a kilogram is. A kilogram of body fat stores about 7,700 calories (a pound, about 3,500). A steady 500-calorie daily gap therefore shifts about half a kilogram a week at first. The rate slows as you get lighter, because a lighter body burns less; anyone who promises a straight line is selling one.⁷
3. Where the calories hide. Drinks (juice, milky coffees, alcohol, soft drinks), cooking oil and dressings (a tablespoon of oil is about 120 calories), and anything ultra-processed, which is engineered to be eaten past fullness.
4. What does not matter. The clock: calories at 9pm are metabolized exactly like calories at noon; late eating is usually extra eating, not slower eating. Meal frequency: three meals, five, or two produce the same result at the same total. Breakfast: optional. Carbohydrates as such: not fattening; the total is.
5. What the number is for. If you are not trying to change your weight, you do not need to count anything. Eat the pattern above and let hunger do the arithmetic; it is quite good at it when it is not being gamed by a food scientist.

Fat, insulin and the machine

Two hormones get blamed for everything. Insulin is not the villain: if you are not diabetic, your blood sugar is supposed to rise when you eat carbohydrate, and insulin is supposed to bring it down. That is food working. What harms is chronic insulin resistance, which comes with excess body fat, inactivity and the ultra-processed pattern, and which improves with movement, sleep, fiber and weight loss. A continuous glucose monitor on a non-diabetic arm measures speed bumps with a seismograph. Cortisol, the other suspect, has its own page: how to handle chronic stress.

The short list of supplements that earn their shelf space

The myths, briefly

When it is more than food

Unintentional weight loss, food that will not stay down, blood where it should not be, or eating that has started to run your life (rules, secrecy, fear of particular foods, eating past pain) are reasons to see a doctor, not to try a new plan. The Body’s Dashboard has the triage; When to Seek Help has the professionals. For personalized advice, look for a registered dietitian, a protected title with a regulated qualification; “nutritionist” is not protected in most countries and can be claimed by anyone with a certificate and a ring light.

¹ World Health Organization, Healthy diet fact sheet: ≥400 g fruit and vegetables, free sugars <10% (ideally <5%) of energy, total fat <30% with saturated <10%, salt <5 g/day. ² Reynolds A et al., “Carbohydrate quality and human health,” The Lancet, 2019: 25–29 g/day fiber, 15–30% lower all-cause and cardiovascular mortality between highest and lowest intakes. ³ Dietary Guidelines for Americans 2025–2030 (1.2–1.6 g/kg); PROT-AGE Study Group, JAMDA, 2013 (older adults 1.0–1.2 g/kg, 1.2–1.5 g/kg if ill or training). ⁴ Dietary Guidelines for Americans 2025–2030, released January 2026. ⁵ Hall KD et al., “Ultra-processed diets cause excess calorie intake and weight gain,” Cell Metabolism, 2019: +508 kcal/day, +0.9 kg in two weeks. ⁶ WHO/Lancet Public Health statement, 2023: no level of alcohol consumption is safe for health. ⁷ The 3,500-calorie-per-pound rule is Wishnofsky (1958); the slowing curve is Hall KD et al., The Lancet, 2011 (dynamic model of weight change). Units: US customary in the books; metric here because the guidelines are.