Losing Weight Safely and Keeping it Off

How fast should you lose weight?

Slowly. The CDC says people who lose weight at a gradual, steady pace — about 1 to 2 pounds, or roughly 0.5 to 1 kg, a week — are the ones most likely to keep it off. The NHS gives the same target. Goals like losing 20 pounds in two weeks are exactly what the CDC warns against, because they set you up to give up.

Do you have to lose a lot for it to matter?

No, and this is the most encouraging fact in the whole subject. Losing just 5% of your body weight makes a measurable difference. For someone weighing 200 pounds (about 91 kg), that is 10 pounds. According to the CDC, that much loss can lower the risk of heart disease, prediabetes and type 2 diabetes, and can improve blood pressure, cholesterol and blood sugar levels.

How do you know if your weight is a health risk?

Body mass index (BMI) compares weight to height. The NHS uses a BMI of 25 to 29.9 for overweight and 30 or more for obesity. Those cut-offs are lower for people of South Asian, Chinese and some other backgrounds, because health problems begin at a lower weight: 23 to 27.4 counts as overweight and 27.5 or more as obesity. If you are of South Asian background, use the lower set of numbers.

Extra weight raises the risk of type 2 diabetes, heart disease, stroke, high blood pressure, some cancers, osteoarthritis and fatty liver disease. The NHS notes that obesity can shorten life expectancy by 2 to 10 years, and often brings breathlessness, tiredness and joint pain long before that.

How many calories do you need?

As a rough guide, the NHS says women use around 2,000 calories a day and men around 2,500. Eating somewhat less than you use is what produces weight loss. Your own number depends on your size, age and activity level, so treat these figures as a starting point, not a rule.

How much activity is enough?

The NHS suggests being active for 45 to 60 minutes a day while you are trying to lose weight, and says you can split that into shorter sessions. A 15-minute walk in the evening counts toward it. The CDC's suggestion is to try several things — walking, swimming, sports, group classes — until you find something you will still be doing in six months.

What actually keeps the weight off?

The CDC's advice for long-term success is about habits rather than any particular diet:

• Write down why you want to lose weight, and keep the list somewhere you will see it.
• Track what you eat, how much you move and how you sleep.
• Set specific short-term goals instead of vague ones. "Walk 20 minutes after dinner, five days a week" works better than "exercise more".
• Find support — family, friends, or a health professional.
• Reward yourself with something that is not food.
• Revisit your goals as you go and adjust them based on real progress.

Sleep is part of the picture too, and the CDC suggests avoiding caffeine after the afternoon.

When to see a doctor

Speak to a doctor before you start if you have diabetes, heart disease, high blood pressure or any long-term condition, or if you are pregnant or breastfeeding. A weight plan that ignores an existing condition can do harm.

See a doctor promptly if:

• You are losing weight without trying to.
• Weight loss comes with fever, night sweats, or blood in your stool or urine.
• You feel faint, dizzy or unusually weak while cutting back on food.
• You are skipping meals severely, making yourself vomit, or your eating feels out of your control.
• Breathlessness, chest pain or joint pain is limiting what you can do in a normal day.

For chest pain, severe breathlessness or fainting, call Rescue 1122 where available, or go to the nearest hospital emergency department.