Manual laborers then, as now, were more likely to be fat.

Physical labor is not related to obesity.

There is a relationship between exercise and weight but not nearly as big as people like to believe. You're right that diet has a much bigger impact.

I had to dig out this paper the other day because someone that I was talking to did not want to believe that weight is mainly tied to one's diet:

http://www.nature.com/?file=%2Fijo%2Fjournal%2Fv21%2Fn10%2Fa...

I'm not sure if this is behind a paywall (my uni has access to everything on Nature's site), so here is the salient bit:

RESULTS: Primarily, subjects aged 40 y have been studied (39.5±0.4 y, mean±s.e.m.) who are only moderately obese (92.7±0.9 kg, 33.2±0.5 body mass index (BMI), 33.4±0.7% body fat); for short durations (15.6±0.6 weeks). Exercise studies were of a shorter duration, used younger subjects who weighed less, had lower BMI and percentage body fat values, than diet or diet plus exercise studies. Despite these differences, weight lost through diet, exercise and diet plus exercise was 10.7±0.5, 2.9±0.4* and 11.0±0.6 kg, respectively.

That seems counter-intuitive to me. Do you have a source?

I don't have a source, but when I worked construction during the summers, I would get fatter while also gaining muscle mass. I always felt hungry after working during the day and would consume massive amounts of calories.

I work in construction, my weight is currently balanced at around 260lbs and I'm around 5'9". By body mass index I'm way beyond morbidly obese. By waist-to-hip ratio for a man I'm way past what's recommended for men - I'm way past on the healthy side.

Here's the funniest thing, and the prime reason why the BMI is totally useless for measuring obesity. I immigrated to Canada, and passed a full physical. My pulse is 60bpm (I actually hit full-blown bradycardic of <50bpm when I lived in the UK), my blood pressure was 125/80. But I'm allegedly morbidly obese.

I can lift 200+ lbs, I can climb a 20' ladder without getting out of breath when most skinny people I know get out of breath going up a flight of stairs (incidentally I live on the 11th floor of an apartment building and I started running out of breath at the 7th floor racing with my dog).

I can eat a double bigmac, large fries, large drink and two burgers off the dollar menu. I can do it regularly and it doesn't effect my weight. I've gone on diets eating mostly salad and calorie restricting myself, and it doesn't effect my weight. The only diet that genuinely works to make me lose weight has been the Atkins, and even coming off of the diet, my weight remains stable at that point like I reset my weight slider or something.

I get told by doctors who are flabbier than myself that I need to lose weight and all I can think is "I can Hulk-throw your fat ass out of your office window and you're struggling walking around the exam table with a coffee".

The obesity epidemic is a product of medical organizations adopting the BMI as a weight reference when it was deemed too inaccurate to study the weight changes in soldiers and was dropped. That was a height and age restricted group, and the BMI couldn't produce usable results to demonstrate fitness. So why medical organizations around the world have adopted it as a holy grail just clearly demonstrates their incompetence.

The other factor is increased sedation, but this isn't necessarily causing obesity. This is causing a general and whole shift in our society to being fat. I'm not talking obesity as a contagious disease, I'm talking that people are probably on average 30-40lbs heavier than what they should be.

Although, it should be noted that most western societies are facing a much more frightening anorexia and bulimia epidemic. Why is it more frightening? Because I'm 80lbs over the male long held 'average' of 180lbs, and likely 120+lbs past what my ideal is allegedly for my height. I can't go 80lbs below my ideal weight, and I certainly can't go 120lbs below my ideal. However I can quite easily go 200, 300, 400lbs above my ideal and have virtually no long term health complications for staying there for a decade and losing the weight. If I was at 60lbs, I would likely be dead or do serious permanent damage to my heart and organs even if I was only there for months and regained the weight.

We wholly don't understand weight in humans. We've got 7 year olds who are anorexic and 7 year olds who are morbidly obese, and no one is doing anything but blaming society when it's happening throughout dozens of cultures.

I agree that BMI is problematic, but that extra weight catches up to you sooner or later. Its extra stress on organs and joints.

By the statistic, underweight and obese have significant increases in mortality. Whilst the overweight (by the BMI) have an overall decrease in mortality compared to the normal weight.

Obesity puts too much pressure on your joints negating the lubricants. But underweight reduces the lubrication in your joints. Overweight seems to be the ideal, as it has for thousands of years.

Obesity is correlated with higher LDL cholesterol, and underweight is correlated with low levels of cholesterol overall, which can reduce vitamin D production and in turn increase your risk to virtually every disease and cancer out there.

For my body fat percentage, I sit in the low 20's, which puts me into the overweight category. Which, incidentally means I'm likely at a reduced risk of stress on my organs and joints, as I've seen little to no evidence of a correlation between muscle mass and arthritis or other weight-related disease.

I don't know about physical laborers being fatter, but our bodies are horribly/wonderfully efficient when it comes to work. The amount eaten will be the larger factor.

See:

http://en.wikipedia.org/wiki/Basal_metabolic_rate#Biochemist.... About 70% of a human's total energy expenditure is due to the basal life processes within the organs of the body (see table). About 20% of one's energy expenditure comes from physical activity and another 10% from thermogenesis, or digestion of food (postprandial thermogenesis).

The reference to the wikipedia article is misleading, and practically false.

Practicing physical activity indirectly increases a series the expenditure for the basal life processes, so it increases the calories consumption more than the raw amount of energy spent doing it.

For weightlifting this is intuitive, because it forces the body to adapt. But for low level continuous activity, like house chores?