Xand van Tulleken

He is descended from Jan van Hoogenhouck Tulleken (1762–1851), a Dutch rear-admiral who was later raised to the nobility with the title of Jonkheer (equivalent of a Squire).

As his descendant, this gives van Tulleken this title as well.

In June 2023, van Tulleken, along with his brother Chris, were the subject of the BBC genealogy programme Who Do You Think You Are?, in which they learned that Jan van Hoogenhouck Tulleken's father, Ambrosius Tulleken, was a wealthy slave-trader who had a plantation in Demerara in The Guianas.

He went to both Hill House preparatory school, and then King's College School, an independent day school for boys in Wimbledon, London, with his twin Chris.

He then went to Somerville College at the University of Oxford.

There he studied medicine, specialising in tropical medicine.

Jonkheer Alexander "Dr. Xand" van Tulleken (born 18 August 1978) is a British doctor and TV presenter.

He is best known for presenting the CBBC children's series Operation Ouch! with his identical twin brother Chris, and the Channel 4 show How to Lose Weight Well.

Van Tulleken has presented many documentaries, including an episode of Horizon discussing male suicide and a BBC programme on the European migrant crisis.

He can often be seen offering up his own body for science experimentation in diet show How to Lose Weight Well, as well as in BBC Horizon episodes "Sugar vs Fat" and "Is Binge Drinking Really That Bad?"

As of July 2023, he was appearing regularly on the BBC1 weekday programme Morning Live, providing a variety of medical advice.

Van Tulleken is also a member of the "Made of stronger stuff" podcast on BBC Sounds.

Van Tulleken is married to doctor Dolly Theis, a visiting researcher at MRC Epidemiology Unit, University of Cambridge and former Conservative Party candidate for Vauxhall in the 2017 general election.

He has one son from a previous relationship.

The van Tulleken twins often appear on shows together, but also both have individual appearances on various programmes.