Hugh Montgomery, director of the University College London Institute for Human Health & Performance, talks about the space where climate, health, and international security meet. Christabel Owens, head of mental health research at the Devon Partnership NHS Trust, explains why warning signs for suicidal thoughts may not be visible to those best placed to spot them.

In 2001 Portugal abolished all criminal penalties for personal possession of drugs – effectively decriminalising their use. Health journalist Nigel Hawkes talks to João Goulão, Portugal’s drug tsar, to find out how effective this policy change has been.

Also, the General Medical Council is introducing revalidation for doctors. Part of that revalidation will require input from a doctor’s colleagues and patients. We hear from John Campbell, Peninsula College of Medicine and Dentistry, about possible independent factors that could affect the scores.

One way of tackling obesity is by attending a weight loss club, such as WeightWatchers . There are many such schemes available on the NHS, but which one is the most effective? We find out the results of an RCT that aims to find out. Also this week, ethnographic studies aren’t just limited to lost tribes. We find out what observation of receptionists in general practice surgeries uncovered.

Tessa Richards (BMJ’s analysis editor) and Duncan Jarvies (BMJ’s multimedia producer) talk to Veena Rao (adviser at Karnataka Nutrition Mission, India) about the issue of undernutrion in the country.

And David Payne (BMJ’s web editor) gives us a run-down of the new bmj.com.

Mariana Lazo, from Johns Hopkins Bloomberg School of Public Health, tells us how non-alcoholic fatty liver disease has affected all cause mortality in the US. Also, Ley Sander, from University College London, discusses the problem of sudden death in epilepsy.

This week’s podcast is from UKSEM, the big sports and exercise medicine conference in London. Daniel Lieberman, an evolutionary biologist from Harvard, explains how we have evolved to run. Steven Blair, University of South Carolina, explains how physical inactivity is having serious effects on our health. Finally Karim Khan, BJSM’s editor, tells us how much exercise gives you the most bang for your buck.

If you’re interested in sports medicine, then have a listen to the BJSM podcast, where your can find more interviews with world leaders in sports medicine - http://podcasts.bmj.com/bjsm

To mark World AIDS Day, the WHO has issued a report outlining policy successes and failures in the diagnosis and treatment of HIV/AIDS. Yves Souteyrand, the co-ordinator of the report, joins us to discuss its findings and how to combat the disease in the future.

Alan White, professor of men's health at Leeds Metropolitan University and the author of a new European report into men's health, explains why we need to look at men differently.

Finally, renowned surgeon Atul Gawande launches the BMJ's 2011 Christmas appeal, in aid of charity Lifebox, by describing how a cheap reliable pulse oximeter costing £160 should be available in all operating theatres. You can donate at www.lifebox.org/donations

How much does it cost sub-Saharan countries to train all the doctors who end up working in the UK, US, Canada, and Australia? Edward Mills from the University of Ottawa explains his economic analysis of healthcare migration. Also Hungarian health minister Miklós Szócska talks about his country's challenges and plans when it comes to improving health outcomes, currently among the worst in Europe.

Vanessa Whitburn, editor of BBC Radio 4’s The Archers, talks morbidity and mortality in Ambridge. James Raftery, University of Southampton, updates the Forrest Report – whose evidence prompted the breast cancer screening programme in the UK.

Somehow we've come to the end of another year. The Independent's health editor Jeremy Laurance talks us through the big health stories from 2011.

And Greg Scott discusses his Christmas paper on the phrase "obs stable", and what it's revealed these two words have actually come to mean to hospital doctors.