Common health questions, answered

There are three useful numbers. The minimum for healthy adults is 0.83 g per kg of body weight a day (WHO/FAO/UNU), about 58 g at 70 kg. Newer research using more precise methods suggests about 1.2 g per kg (about 84 g at 70 kg) is a better everyday target. If you strength-train or are losing fat, aim for about 1.6 g per kg (about 112 g at 70 kg). Beans, lentils, yogurt, tofu, milk, eggs, fish and chicken can get you there without supplements. If you have kidney disease, ask your doctor first.

Source — WHO/FAO/UNU Technical Report 935 (2007); Humayun et al., American Journal of Clinical Nutrition (2007); Morton et al., British Journal of Sports Medicine (2018)

No. You can't target fat loss to one area. In a controlled study, six weeks of abdominal exercises didn't reduce belly fat. Crunches strengthen the muscle underneath, but the fat on top only goes down when your overall body fat goes down. That happens through a steady calorie deficit, enough protein, daily walking and strength training.

Source — Vispute et al., Journal of Strength and Conditioning Research (2011)

Adults should get at least 7 hours a night, according to the American Academy of Sleep Medicine; the National Sleep Foundation recommends 7–9 hours. Short sleep has measurable effects. In studies of healthy young men, two nights of short sleep raised hunger hormones and appetite, and one week of 5-hour nights lowered daytime testosterone by 10–15%.

Source — Watson et al., Sleep (2015); Spiegel et al., Annals of Internal Medicine (2004); Leproult & Van Cauter, JAMA (2011)

Do both. In an eight-month randomised trial, cardio produced more fat loss than weights alone, while weights built muscle. The combination gave the best overall result: it lost fat and gained muscle. The WHO recommends 150–300 minutes of moderate aerobic activity a week plus strength training on two or more days.

Source — Willis et al., Journal of Applied Physiology (2012); WHO physical activity guidelines (2020)

European Food Safety Authority guidance puts total daily water intake for adults at about 2.5 litres for men and 2.0 litres for women. That includes water from food, which typically provides around a fifth of it. You'll need more in hot weather or when you sweat a lot. A practical check is pale-yellow urine and rarely feeling thirsty. People with heart or kidney conditions may have limits set by their doctor.

Source — EFSA Scientific Opinion on Dietary Reference Values for water (2010)

Yes. You can look slim and still carry excess fat around your abdomen, with insulin resistance, high blood sugar, cholesterol or blood pressure. Risk at a given weight also depends on ancestry: people of South and East Asian descent tend to develop diabetes and heart disease at lower body weights, which is why the WHO uses a lower BMI cut-off for them (23 rather than 25). Get these checked whatever your size.

Source — WHO Expert Consultation, The Lancet (2004); AHA scientific statement on South Asians, Circulation (2018)

Yes. What matters most for building muscle is getting enough total protein alongside strength training. Vegetarian sources such as beans, lentils, tofu, yogurt, milk, eggs and peanuts can provide it. Combining grains with beans or lentils, like beans with rice or lentil soup with bread, improves protein quality because each supplies amino acids the other lacks. Soy foods are especially dense in protein: textured soy protein has about 50 g per 100 g dry.

Source — Academy of Nutrition and Dietetics position paper on vegetarian diets (2016); FAO protein quality report (2013); Morton et al., British Journal of Sports Medicine (2018)

Break it up. In a controlled study, 2 minutes of light walking every 20 minutes lowered blood sugar and insulin after meals, and short walks after eating also help. Being active overall matters too: a Lancet analysis of over a million people found that 60–75 minutes a day of moderate activity, such as brisk walking, largely offset the extra risk linked to long sitting.

Source — Dunstan et al., Diabetes Care (2012); Ekelund et al., The Lancet (2016)