There is a ''looming health crisis'' facing England as the vast majority of people entering old age are overweight, Hampshire experts have said.
New figures show that almost three quarters of people aged 45 to 74 in England are either overweight or obese.
Young adults are the only age group which have a normal average body mass index (BMI), according to new figures from the Health and Social Care Information Centre (HSCIC).
The National Obesity Forum warned that figures showed a large proportion of the population will face significant problems as they enter old age.
Being overweight or obese can lead to a number of potentially life-threatening conditions including type 2 diabetes, coronary heart disease, some types of cancer, such as breast cancer and bowel cancer, and stroke.
Commenting on the figures, Tam Fry of the National Obesity Forum said: ''These figures show that there is a looming health crisis for the nation.
''If you think that obesity is just for the young and the middle aged then you are wrong.
''There needs to be a clear message that everybody needs to take control and watch what they are eating.''
He warned that many overweight elderly people are in a ''catch 22'' situation because they are suffering a combination of problems linked to being overweight and muscle wastage - so they cannot exercise to improve their health.
The HSCIC figures show that there is a rising tide in the proportion of people who are overweight or obese.
At least seven in ten people in England aged 45 and over are either overweight or obese.
And the average BMI measurement of those aged 45 to 74 stood at 28.3 - those with a BMI of 25 to 29.9 are considered to be overweight.
Professor Martin Severs, a geriatrician from Portsmouth and HSCIC lead clinician, said: ''Obesity is going to have a lot of short to medium effects around diabetes and heart disease.
"And then you have got long term issues because your body will be carrying around a lot more weight, you then go on to suffer problems such as arthritis and having difficulty breathing. There is a whole set of second-order things as a consequence of weight.''
When asked what impact the growing number of overweight and obese older people will have on society, he said: ''There are potentially a number of scenarios, one is that you get less older people because they get illnesses (as a result of) obesity younger and therefore there is a mortality effect.
''The second possibility is that the life expectancy of older people plateaus and starts to drop.
''The third possible interpretation is that the disability-free life expectancy starts to shorten. But I don't have enough evidence to say which one or combination of those scenarios could happen.''
Charity Age UK warned that public health measures are mostly aimed at younger and not older people.
Ruthe Isden, health influencing programme director at the charity, said: ''Historically public health approaches have been very focused on children and it's all about getting them while they are young and if you are old then 'it's a bit late to bother'.
''There is a really important need to turn some of that around and actually start talking to people about how it's never too late to adopt healthy behaviours.''
She said just a ''tiny'' proportion of older people get the recommended amounts of exercise, adding: ''In the 75-plus population it's something as low as 4% of people getting their recommended weekly amounts of exercise so we do have a really big issue here with obesity and inactivity.''
The new HSCIC data, which focuses on the health and care of older people also shows that the population aged 65 and over is rapidly rising.
In 1951, 4.5 million people were aged 65 and above but by 2051 this number is expected to rise to 16.6 million.
While people in this age bracket account for just one in six of the population, they take up one in every two hospital beds, the figures show.
Janet Morrison, chief executive of charity Independent Age, said: ''These figures show that older people are the main users of the NHS and are most likely to be affected by any cuts in services as a result of funding problems. If we are going to expect more older people to get treated outside of hospital, we need realistic levels of funding for councils to provide community care''.
Dr Alison Tedstone, chief nutritionist at Public Health England (PHE), said: ''There is no easy answer to reducing obesity; it is a complex issue that requires action at individual, family, local and national levels. Being overweight or obese increases the risk of developing type 2 diabetes, heart disease and certain cancers.
''Excess weight can also be associated with low self-esteem and mental health issues. PHE is committed to helping tackle overweight and obesity in adults of all ages through a range of approaches that support action on the local environment to make eating less and being more physically active easier, with many local authorities already working hard to achieve this.''
The proportion of people entering old age being either obese or overweight could lead to a ''health crisis'', experts have warned.
The below figures show the proportion of the population in different age groups who are overweight or obese, and the average body mass index (BMI) of people in that age bracket.
People are deemed to be of normal weight if they have a BMI score of 18.5 to 24.9 and overweight with a score of over 25.
Those with a BMI over 30 are deemed to be obese.
- 36% of people aged 16 to 24 are either overweight or obese. People in this age group have an average BMI score of 24.5.
- 51% of people aged 25 to 34 are either overweight or obese. People in this age group have an average BMI score of 26.1.
- 64% of people aged 35 to 44 are either overweight or obese. People in this age group have an average BMI score of 27.3.
- 72% of people aged 45 to 54 are either overweight or obese. People in this age group have an average BMI score of 28.3.
- 73% of people aged 55 to 64 are either overweight or obese. People in this age group have an average BMI score of 28.3.
- 73% of people aged 65 to 74 are either overweight or obese. People in this age group have an average BMI score of 28.3.
- 70% of people aged 75 and over are either overweight or obese. People in this age group have an average BMI score of 27.6.