Bone health while losing weight: calcium, vitamin D and load

SASian Anderson, Writer and editor, MyGLP. Sources checked 21 October 2026.

Why weight loss touches bone

Bone responds to load. Carrying more weight loads it more, and when weight comes off, some of that signal goes. Studies of large weight loss, from diets and from surgery, show a small drop in bone density at the hip over the first year or two. The weight loss medicines have not been shown to harm bone beyond that effect of the weight loss itself, but the trials were not long enough to be sure either way.

For a woman in her 20s or 30s with a healthy skeleton, the drop is small and recovers. For a woman after the menopause it lands on top of the fastest bone loss of her life. The Royal Osteoporosis Society says women can lose up to 10% of bone density in the five years after periods stop.

Calcium: 700mg a day from food

The UK reference intake for adults is 700mg of calcium a day. On a small appetite it is easy to fall short, because dairy portions shrink with everything else.

Calcium tablets are only for women who cannot get there with food. Ask a GP first, since high-dose calcium supplements have been linked to kidney stones and the benefit to bone is small when food intake is adequate.

Vitamin D: 10 micrograms from October to March

Calcium cannot get into bone without vitamin D, and the UK sun makes none in the skin between October and March. The NHS advice is for every adult to take 10 micrograms, which is 400 IU, a day through autumn and winter, and all year if you are rarely outdoors, cover your skin, or have darker skin. A year's supply costs under £5. Do not take more than 100 micrograms a day without medical advice.

Load: the exercise that counts

Swimming and cycling are good for the heart and do little for bone. Bone needs impact and muscle pull. The UK Chief Medical Officers recommend strength exercise on two days a week for every adult, and the Royal Osteoporosis Society adds that brisk walking, stairs, dancing and small jumps all load the hip and spine. The strength guide shows the moves, and the walking guide covers the easy half.

Who should ask for a scan

A DEXA scan measures bone density in ten minutes and is free on the NHS if you qualify. NICE guidance says to assess fracture risk in women aged 65 and over, and in younger women with a risk factor. Ask your GP about a scan if any of these apply:

• Periods stopped before 45, or you had both ovaries removed.
• A parent broke a hip.
• You have taken steroid tablets for 3 months or more.
• You have broken a bone from a fall at standing height.
• Your BMI has been under 19 at any point, or you have had an eating disorder.
• You have coeliac disease, an overactive thyroid, rheumatoid arthritis or early menopause.
• You have lost a large amount of weight after the menopause.

Other things that eat bone

Smoking, more than 14 units of alcohol a week, long-term proton pump inhibitors for reflux, and some epilepsy and breast cancer medicines all thin bone. A low body weight is itself a risk, which is one reason to stop losing when you reach a healthy range rather than pushing on.

Sources

1. Bone health (Royal Osteoporosis Society)
2. Calcium: vitamins and minerals (NHS)
3. Vitamin D (NHS)
4. Osteoporosis: assessing the risk of fragility fracture (CG146) (NICE)
5. UK Chief Medical Officers' physical activity guidelines (Department of Health and Social Care)