Generations are generally useless, aside from marketing plans. The Baby Boom happened in 1946, after soldiers returned home from war (the occupying soldiers came from a different, supplemental draft so they often already had kids) and it was later that marketing groups changed them into a generation stretching to 1964 and even 1965.

'Generations' had been used prior to that but they were 20 years rather than 18 or 19 and based on Europeans in America - so when the 13th generation came along, and 13 was considered an unlucky number, they became Generation X. But there was overlap in that because the Baby Boom was not yet the anchor point of generation-speak, it was simply an event. Thus, we have cultural oddities like that Billy Idol was the lead singer of the band Generation X even though he was born in 1955. Then we got Lost Generations, Generation Y, Millennials.

One thing that seems clear in Australia - if current trends continue, Australia's Generation X will overtake Baby Boomers for poor health, including rates of obesity and diabetes. That will have huge implications for healthcare.

University of Adelaide researchers compared the health status of their range of Baby Boomers (born from 1946–1965) and Generation X (1966–1980) at the same age range of 25-44 years. They found Generation X had significantly poorer levels of self-rated health, and higher levels of obesity and diabetes compared with Boomers, with no real difference in physical activity between the two groups.

Click image. Logistic regression analysis of the association between overweight and obesity (BMI≥25.00) and generation membership of Generation X (aged 25–44 years 2007/08 NHS data) and Baby Boomers (aged 25–44 years 1989/90 NHS data) using data from the Australian Bureau of Statistics. doi:10.1371/journal.pone.0093087

"Generation X appears to have developed both obesity and diabetes much sooner when compared with Baby Boomers, which is a major concern on a number of fronts," says co-author and University of Adelaide PhD student Rhiannon Pilkington.

Generation X is more than twice as likely to be overweight or obese and have diabetes at 25 to 44 years of age, compared to Baby Boomers at the same age in 1989.

The prevalence of obesity in men is nearly double, with 18.3% of Generation X males obese compared to 9.4% of Baby Boomers at the same age. The gap is not as profound for women, with 12.7% of Generation X females classified as obese compared to 10.7% of Baby Boomers at the same age.

"This study adds to the growing evidence world wide suggesting that each younger generation is developing obesity and related chronic health conditions earlier in life," Ms Pilkington says.

"Although the two groups in our study did not seem to have any difference in levels of physical activity, our lifestyles and food environments have changed drastically over recent decades.

"Transport options and workplaces encourage sedentary behavior, and food high in fat and sugar is often more readily available than a healthier alternative. This may account for why the younger generation is developing unhealthy weight levels at an earlier age," she says.

Ms Pilkington says that together, Baby Boomers and Gen X form almost 77% of Australia's workforce.

"There is the potential for obesity-related health problems to propel many from the workforce early, or to drastically reduce their ability to work. If ongoing generations continue down this path of developing what were once considered to be age-related conditions earlier in life, the consequences for healthcare costs will be enormous."