OSAIA Health

Weight loss and bone health

Weight loss and bone health are connected. Learn how to look after both safely, and when you should contact a specialist.

Why it matters: the link between weight and bone health

Weight plays a bigger role in your bones than most people think. The skeleton is strengthened by the daily load of your body weight, but being significantly underweight and losing weight quickly can both do more harm than good. If you lose weight too fast, you lose not only fat but also bone mass and muscle.

Risk zones: when does your weight affect bone health?

Knowing where the risks are helps you make informed choices about your weight-loss plan.

  • Rapid weight loss

    Losing more than 1 kg a week speeds up bone loss. That applies whatever the method, including GLP-1 medicines such as Ozempic and Wegovy. The right support with diet and supplements is essential.

  • Low body weight

    A BMI under 18.5 is an independent risk factor for osteoporosis. A low body weight means less mechanical load on the bones, and often lower oestrogen. Both speed up bone loss.

  • Nutritional gaps

    Restrictive diets often cut the intake of calcium, protein and fat, all of which the bones need. Calcium and vitamin D deficiency is common among people who are actively dieting.

How to lose weight in a way that protects your bones

  • Lose weight gradually

    No more than 0.5–1 kg a week

  • Keep your calcium intake up

    1,000–1,200 mg a day, and do not cut out dairy products

  • Eat enough protein

    To protect muscle and bone. Aim for 1.2–1.5 g per kg of body weight

  • Include weight-bearing exercise

    It stimulates bone formation and helps you keep muscle

  • Get enough vitamin D

    Especially important if you are eating less and getting less sun

  • Avoid a very low-calorie diet

    Under 1,200 kcal without medical guidance

Did you know?

Weight-bearing exercise does two jobs while you lose weight: it burns calories, and it sends the mechanical signals your bones need in order to stay dense. Strength training 2–3 times a week is one of the best ways to protect your bones while you lose weight.

When should you have your bone health checked?

Consider an assessment of your bone health if one or more of the following applies to you:

  1. 01

    You have lost more than 10% of your body weight in the past year

  2. 02

    You have started weight-loss medication, for example a GLP-1

  3. 03

    You have had weight-loss surgery

  4. 04

    You are postmenopausal and actively trying to lose weight

  5. 05

    Your BMI is under 20

Want to strengthen your bone health day to day?

With the OSAIA app you get expert knowledge, personal recommendations and tools, built to help you take the right steps for your bone health every day.

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Frequently asked questions

Answers to the questions we hear most often about weight loss and bones.

  • Can weight loss weaken my bones?

    Losing more than 1 kg a week speeds up bone loss, whatever the method, including GLP-1 medicines such as Ozempic and Wegovy. Restrictive diets often reduce the intake of calcium, protein and fat, and a lack of calcium and vitamin D is common among people who are actively dieting.

  • How fast is it safe to lose weight?

    Aim for no more than 1 kg a week, and do not eat fewer than 1,200 kcal a day without medical guidance. A BMI under 18.5 is itself a risk factor for osteoporosis, because a low body weight means less mechanical load on the bones and often lower oestrogen.

  • How do I lose weight without harming my bones?

    Get 1,000–1,200 mg of calcium a day, and do not cut out dairy products. Eat 1.2–1.5 g of protein per kg of body weight to protect muscle and bone. Make sure you get enough vitamin D, and do strength training 2–3 times a week while you lose weight.

  • When should I have my bone health checked?

    Consider an assessment if you have lost more than 10% of your body weight in the past year, have started weight-loss medication such as a GLP-1, have had weight-loss surgery, or are postmenopausal and actively trying to lose weight.

Keep learning

Explore related topics to get a better understanding of bone health.

  • Menopause and bone health

    Learn how menopause affects bone health, and what you can do to protect your bones during this transition.

    Read more

  • Nutrition and bone health

    What you eat affects your bones more than you might think. Explore our nutrition section and learn how the right diet can help prevent bone loss.

    Read more

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