With a new mathematical model, researchers are able to explain how different levels of diversity in gut microbes lead to different responses to diets.

A battle is brewing in Washington as the capital city prepares to regulate personal fitness trainers in a move that could ripple through the country’s booming $24 billion gym industry and its fight against flab. The District of Columbia, whose residents are generally fitter than the rest of the country, is set to adopt the United States’ first regulations on trainers, following a law passed by the city council last year. It named an obscure city regulatory panel, the Board of Physical Therapy, to develop rules for trainers who help guide exercise aficionados through their stretching, weightlifting and crunches.

New research has shown for the first time that the part of the brain used for learning, memory and mental health is smaller in people with unhealthy diets.