Young men who are obese appear to have lower sperm counts than their slimmer peers but it’s not certain whether obesity can hamper a man’s chance of becoming a father.

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A new study, reported in the journal Fertility and Sterility, has added to evidence linking obesity to poorer quality sperm.

For years researchers have found a link between sleep deprivation and obesity and a new study has found that sleeping less may make you eat more.

Much of the previous research has looked at people with a high BMI (body mass index) but French researchers have found that shortened sleep gives normal-weight men the munchies too.

In fact, cutting their sleep time from eight hours a night to four hours resulted in the participants wolfing down a Big Mac’s worth of extra calories during the day.

A hormone that plays a major role in preventing people getting fat may also help guard against Alzheimer’s disease, new research suggests.

Leptin, which was only discovered back in 1994, helps regulate people’s appetite and gives them signals that tell them they are “full”, stopping them from over-eating.

Studies have shown that obese people tend to have lower levels of leptin or are resistant to it in much the same way diabetics are resistant to insulin.

A Massey University scientist’s research on spider monkeys has uncovered one of the reasons for the obesity epidemic – the lack of protein in most modern foods causes people to overeat.

Nutritional ecologist Professor David Raubenheimer took part in a study that found that when protein-rich foods were scarce, the Bolivian rainforest spider monkey ate greater amounts of low protein/high carbohydrate foods to keep up its protein intake.

This led to a massive increase in energy consumption.

People who are overweight – but not obese – tend to live longer than people who are underweight or normal weight, according to a new study.

The Canadian study was published in the online journal Obesity, and found that people who were underweight or extremely obese (based on their body mass index or BMI) died the earliest reports WebMD.