How to stay healthy: the short list that the evidence supports

Health advice is crowded because each new study gets a headline. The underlying picture has been stable for decades. A small number of habits account for most of the difference in how long people live and how well. None of them is new, and none needs a product.

The study most people quote

In 2018, researchers at Harvard pooled two long-running cohorts of US health professionals, the Nurses' Health Study and the Health Professionals Follow-up Study, and looked at five low-risk habits: never smoking, a body mass index of 18.5 to 24.9, at least 30 minutes a day of moderate to vigorous activity, moderate alcohol intake, and a diet quality score in the top 40 percent. They then projected life expectancy at age 50 for people who had none, some or all five.

Two cautions. These are observational studies, so they show association, not cause: people who do all five things differ in other ways too. And the 12 to 14 years are model projections, not lifespans anyone measured. Still, the direction is consistent across many cohorts and countries, and the trials that have tested the individual habits (exercise, diet, sleep) mostly agree with it.

1. Do not smoke

Never smoking was one of the five factors. If you smoke, stopping is the change with the longest record of benefit in medicine, and a clinician can go through the support and medication options with you.

2. Move most days, and lift twice a week

The US Physical Activity Guidelines and the WHO both set the same baseline for adults: 150 to 300 minutes a week of moderate activity (brisk walking counts), or 75 to 150 minutes of vigorous activity, plus muscle-strengthening work on two or more days a week. The guidelines say plainly that the people who do the least gain the most from small increases. Our guides to daily steps, cardio and strength training go into the detail.

3. Eat mostly whole foods, with enough protein and fibre

The 2025 to 2030 Dietary Guidelines for Americans, released in January 2026, ask for protein at every meal (1.2 to 1.6 grams per kilogram of body weight a day), three servings of vegetables and two of fruit on a 2,000 calorie pattern, two to four servings of whole grains, saturated fat under 10 percent of calories, and much less highly processed food and added sugar. Under the details, the cohort data point the same way: more whole grains, vegetables, fruit, nuts, legumes and fish, less processed meat and sugary drinks. See protein, fibre and the sample week of meals.

4. Sleep seven hours or more

The American Academy of Sleep Medicine and the Sleep Research Society recommend at least seven hours a night on a regular basis for adults. Short sleep raises appetite in controlled studies and is linked to higher risk of weight gain, diabetes and heart disease in cohorts. The sleep guide has the trial numbers.

5. Drink less, if at all

The Li study counted moderate drinking as low risk. The evidence has moved since. A 2023 meta-analysis of 107 cohorts found no significant mortality benefit from low-volume drinking once study biases were adjusted for, and the new US guidelines simply say to consume less alcohol for better overall health. The alcohol guide covers what changed.

6. Keep weight in a healthy range, and keep it there

Body weight was one of the five factors. For many people the hard part is not losing weight but keeping it off. The weight maintenance guide covers what the National Weight Control Registry found and what the GLP-1 withdrawal trials show. If you are on a GLP-1, what to eat and how to keep muscle are the two places to start.

What does not make the list

Very little else has evidence on this scale. Supplements, detoxes, cold plunges and single superfoods have nothing like the cohort data behind the habits above. That does not make them harmful, only unproven by comparison. If you have time and attention for five changes, spend them on the five above.

Where to start

Pick the habit with the most room. If you walk 3,000 steps a day, the gain from 6,000 is larger than the gain from perfecting your diet. If you sleep five hours, that comes first. A small, specific change you can measure, such as 2,000 more steps a day or a bedtime 30 minutes earlier, is easier to hold than a vague one. If you have a medical condition, check the plan with your clinician first.

Logging it

Each of these habits is easier to change when you can see it. Peptide AI puts food, training, sleep and steps on one timeline: meals in nutrition tracking, sessions in the training log, sleep and steps from a watch or ring through wearable integrations, and labs in bloodwork tracking. Four weeks of that log usually shows which habit to work on next.