Life Expectancy in the USA, Formula - you calculate from your present age, not your birth age.

Yes, you hit the nail on the head. Staying thinner than average is one of things my 99 year old Uncle mentioned as an attribute to his longevity.
Can you imagine the USA, thinner than average is most likely weighing what you are supposed to weigh according to the BMI. After all 70% of Americans are overweight.
This is a fascinating subject, one that just came to light in my mind based in another unrelated thread.
There is always this constant debate in the USA when to collect Social Security, how long will you live.

We all know in rough numbers that the average male in the USA can expect to live to around 79 years old, meaning half will make it to that age.
The thing is, now being retired, one huge detail never reported in the media (I look at the media as entertainment)

If you make it to retirement age then the median death age moves up because the median age of 79 is calculated from birth year 0 to 79 A lot of men die between birth year 0 to 62, 63, 64...70 ... 79
So for example if you make it to the age of 67 your new median death age is 83 if you make it to 83 your new median age is 90
If you retire at 65 your median age to die is now 83 not 79.
Wow, this is cool and one will never find a more reliable source than Social Security Stats.

This is a much more complicated statement depending on what age that you are in life.
It's really interesting and something that taken at face value in the USA isnt as clear cut by the reporting in the media.
According to the USA government chart roughly 50% men from birth to age 80/81 will have died but if you make it to that age your median death age is now much higher. The scale is graduating from birth year 0 to present.

Woman as we know live a few more years in all groups.

I find this fascinating ...
Here is the USA source =

It's not a normal distribution, the average, combined with standard deviation, will give a reasonably clear picture for normal distributions. These are fascinating data.
yeah, if we're so hep on stats today - thinner (no gender difference) live longer.
I am not a stat - just look at it for fun.
I'm an individual.
The chart is for insur co. Those co.s have actuaries for everything as they analyze the financial costs of risk and uncertainty. They use mathematics, statistics, and financial theory to assess the risk of potential events, and they help businesses and clients develop policies that minimize the cost of that risk.
As seen at the grocery store today. I felt confident enough to pick some up. :LOL:

What do they say about lairs and statistics? Sounds like voodoo science. Heredity is the biggest influence, then environment and lifestyle choices. That's why you see 100 year old 2 pack a day smokers as well as marathon runners who drop dead at 50.
Median means half will die sooner and half will live longer. Therefore, the factors you cite are baked into that number already.
It doesn't mean any specific person will die at that age, it means for the population of males or females of a specified age, it will take the specified number of years for half of that population to pass.

It's useful for Social Security as they can estimate how much money they need. It's a bit less useful for any individual because of the factors your cite.

It's a measure of risk or exposure the program has to paying out benefits for a large population, not any one individual.