Now, we consider an 8 hour day in front of the computer as a hard day at work. But eat like we've been working in the fields...
Eating fat does not necessarily make you fat, nor is it in itself a bad at all. Many fats are among the best things for your brain and heart. At the same time, fat-free foods can quite easily be bullshit.
A pound of sugar is fat-free, after all, but has an insane calorific value. (110 per oz)
Sugar is 100% total carbs.
A ounce of feta cheese has plenty of fat, and less calories per ounce than zero-fat sugar (feta is 75 per oz).
Feta cheese is 75% fat, 20% protein, 5% total carbs.
Then I try to show them some fat-free products that nonetheless has immense amounts of sugar and calories.
I think that using this topic as a lead-in has been the most effective way to get my friends to change their diets and consider what they eat.
His basic point is that "food science" doesn't know very much, is heavily politicized, and that we don't really know on a deep level how food, food-like substances, supplements, and so forth work. The war on "fat," as you note, doesn't make much sense because it counts the "fat" from a Big Mac and the "fat" from almonds the same way, which makes little sense. It counts the "sugar" from strawberries and Pepsi the same way. This is, to put it lightly, stupid, and it makes people stupid, since most people hear marketing slogans or public service announcements or whatever and follow those.
I do know that some people have raised issues with his science.
Haven't heard too many complaints about his general takeaways though...
Bodybuilders know a lot about diet, especially in the context of controlling the body fat percentage - mostly because in their case, the diet must work, or else they lose the competition. They can't rely on the latest fad on Oprah's that may or may not actually work. So the stuff they do tends to have a solid reality-based backing.
Any bodybuilder will tell you that low-fat diets are bullshit. Carbs are probably more aggressive fat-builders than fat per se, mostly because carbs are absorbed quickly, while fats are absorbed more slowly.
It's interesting to see the convergence from various sources. E.g., some diets recommended by weightlifters for "maintenance" (only to preserve a certain physique), and the diet recommended by Ray Kurzweil on health and longevity grounds, are similar in that the recommended daily intake of macronutrients is 33% carbs, 33% fat, and 33% protein as percentage of calories, or roughly 2:1:2 in weight.
As a comparison, that's slightly more protein that most people normally eat, a heck of a lot less carbs than the average intake, and a fairly average level of fat intake. I actually did this; reducing carbs was hard at first, but I got used to it after a while. It's amazing just how high you can raise the total caloric intake, if you keep the macronutrients at 33/33/33 relative ratios, without starting to gain fat. I was eating over 3200 cal / day, with 3 hours of lifting weights / week as my only exercise, and I was neither gaining nor losing fat (but I was gaining muscle).
In my mind, there's no doubt: By far the easiest way (in terms of effort spent, hours in the gym spent, etc.) to lose fat is to reduce the total calories by reducing the carbs intake (don't bother with tweaking the fat intake), and lift weights either 2 or 3 times a week, between 30 and 60 minutes each. 2 x 30 is the minimum that produces results, 3 x 60 is the maximum that allows you to keep it up a long time without burning out.
Don't eat carbs below 25% of your daily caloric intake, or you'll start to feel pretty weak. In other words, reduce carbs, but don't be a carbs nazi.
EDIT: This message was edited several times.
In fact eating fat will probably lead to less calories overall since fat gives an earlier feeling of fullness.
That explains why mediterranean and asian diets, which are high on carbs but low on sugar (or artificial fructose), don't cause nearly as much obesity.
See, I can use useless anecdote too...
Your great-grandparents may have lived well into their 90s, but they are the outliers on the curve of lifespans for people born at the same time as them. Most of the variance at this extreme end of the spectrum is entirely due to genetics and not lifestyle (e.g. Donald O'Connor led an active lifestyle, ate well for someone who lived through most of the 20th century, and lived to be 78 which is almost 25 years beyond the average life expectancy for someone born in 1925 -- he also was notorious for smoking several packs (2-5) of cigarettes a day for most of his life; shall we suggest that smoking has no health consequences since I can find examples of people who lived a long time and were also smokers?)
What is more useful is to see what the impact of diet/lifestyle options are on the larger chunks of the population and not use outliers as exemplars for points we might wish to make.