What's worse for us: sugar or fat? To answer the hottest question in nutrition, twin doctors Chris and Xand Van Tulleken go on month long high-fat and high-sugar diets. The effects on their bodies are shocking and surprising. But they also discover that in the debate about fat and sugar, the real enemy might have been hiding in plain sight.

In February 2013, a hole opened up beneath a home in Florida, and swallowed a man. Jeff Bush was asleep when a sinkhole opened up beneath his bedroom. Despite the efforts of his brother to rescue him, Jeff was never seen again and his body was never recovered. Professor Iain Stewart travels to Florida to try and understand what killed Jeff, and why the geology of this state makes it the sinkhole capital of the world.

Horizon goes behind the scenes at Nasa to discover how it is preparing for its most ambitious and daring mission: to land men - and possibly women - on the surface of Mars. It's over 40 years since Neil Armstrong made the first human footprint on the moon. But getting to the red planet would involve a journey of at least three years. Horizon meets the scientists and engineers who are designing new rockets, new space suits and finding ways to help astronauts survive the perils of this long voyage. And it turns out that having the 'right stuff' for a mission to mars might not be quite what you expect.

As they contain no active ingredient, placebo medicines and pills should not really work, but they are now being shown to be effective in helping treat pain and depression and even alleviating some of the symptoms of Parkinson's disease. This programme explores why they work and how everyone could benefit from them.

Horizon uncovers the truth about how you really make decisions. Every day you make thousands of decisions, big and small, and behind all them is a powerful battle in your mind, pitting intuition against logic. This conflict affects every aspect of your life - from what you eat to what you believe, and especially to how you spend your money. And it turns out that the intuitive part of your mind is a lot more powerful than you may realise.

When pioneering developmental psychologist Professor Uta Frith started her training back in the 1960s, she met a group of beautiful, bright-eyed young children who seemed completely detached from the rest of the world. It turned out they had just been given the then-new diagnosis of autism. Uta passionately wanted to know more about these children, and they inspired her to dedicate the rest of her career to studying the autistic mind. On the eve of National Autism Day, Horizon reveals how Uta's lifetime study of people with autism has transformed our understanding of this mysterious condition. In this film Uta shows how people with autism perceive and interact with the world and how, for them, another kind of reality exists. She meets people with autism who have extraordinary talents, and explains why they often fail to understand jokes. She also explores whether many of us could be just a little bit autistic.

To celebrate its 50th birthday, Horizon invites the public to play a role in tackling the greatest challenges facing science today. This special episode of Horizon launches the £10 million Longitude Prize 2014 - a prize developed by Nesta, with Technology Strategy Board as funding partner, to find solutions to a new scientific challenge. The Longitude Prize 2014 commemorates the 300th anniversary of the original Longitude prize - a £20,000 reward for finding a way to determine longitude at sea accurately. The prize was overseen by the Board of Longitude, comprising the scientific, political and naval leaders of the day. A range of possible methods were developed with the Board of Longitude's support, but Yorkshire clockmaker John Harrison was the biggest winner with his marine chronometer clock, which enabled ships accurately and reliably to determine their longitude, avoiding potential shipwreck and enabling Britain's global trade to flourish. Horizon explores six potentia

Horizon tells the inside story of the search for Malaysia Airlines flight MH370. With access to the key players on the frontline in the southern Indian Ocean and the British satellite engineers who tracked the plane's final hours, Horizon breaks open the biggest mystery in aviation history. The film reveals how MH370 disappeared in a radar blind spot; what investigators believe happened to the aircraft in its last minutes; and how the area in which it could be found is still to be searched. Plus Horizon examines the new technologies, like black box streaming and enhanced air traffic surveillance, that mean an airliner should never vanish without trace again.

Over the last few years, our weather in Britain has become more extreme. Last winter was the wettest ever recorded, as deadly storms battered the country for weeks on end. But previous winters have seen bitter lows of -22, as Britain was plunged into a deep freeze. What everyone wants to know now is: why is our weather getting more extreme, can we expect to see more of it in the future, and has it got anything to do with climate change? In this episode of Horizon, physicist Dr Helen Czerski and meteorologist John Hammond make sense of Britain's recent extreme weather and discover that there is one thing that connects all our recent extreme winters - the jet stream, an invisible river of air that powers along 10 km above us. What's worrying is that recently it has been behaving rather strangely. Scientists are now trying to understand what is behind these changes in the jet stream. Helen and John find out if extreme winters are something we may all have to get used to in the

Dr Michael Mosley seeks to establish the truth about meat. Are those barbecue favourites like burgers and sausages really that bad? Should we all go vegetarian instead? Michael uncovers the latest science and puts it to the test on a high-meat diet. Will eating beef and bacon every day be bad for him? What meat should a healthy carnivore be buying?

Dr Michael Mosley examines the impact eating meat has on the planet and finds out what meat eco-friendly carnivores should be buying: free-range organic or factory-farmed meat.

Changes to the bacteria that live inside all of us are responsible for increasing the number of people with allergies, suggests new research. In this episode of Horizon, the show investigates this claim by conducting a unique experiment with two allergic families in order to find out just what it is in the modern world that is to blame. With a raft of mini cameras, GPS units and the very latest gene sequencing technology, the show discovers how the western lifestyle is impacting their bacteria. Why are these changes making people allergic? And what can be done to put a stop to the allergy epidemic?

Twenty-five years after the world wide web was created, it is now caught in the greatest controversy of its existence: surveillance. With many concerned that governments and corporations can monitor our every move, Horizon meets the hackers and scientists whose technology is fighting back. It is a controversial technology, and some law enforcement officers believe it is leading to 'risk-free crime' on the 'dark web' - a place where almost anything can be bought, from guns and drugs to credit card details. Featuring interviews with the inventor of the world wide web, Sir Tim Berners-Lee, and the co-founder of WikiLeaks, Julian Assange, Horizon delves inside the 'dark web'.

The Ebola virus. No-one knows exactly where it comes from but one thing is certain - it's one of the most virulent infections known to science. This special episode of Horizon meets the scientists and doctors from all around the world looking for the cure and hears first-hand accounts of what it's actually like to catch - and survive - this terrible disease.

Dr Michael Mosley and Professor Alice Roberts investigate if male and female brains really are wired differently. New research suggests that the connections in men and women's brains follow different patterns, patterns which may explain typical forms of male and female behaviour. But are these patterns innate, or are they shaped by the world around us? Using a team of human lab rats and a troop of barbary monkeys, Michael and Alice test the science and challenge old stereotypes. They ask whether this new scientific research will benefit both men and women - or whether it could drive the sexes even further apart.