Strength has more to do with how well you can coordinate your muscle fibers than how big they are, and that’s pretty much entirely determined by your central nervous system.
Well, I don’t know where I read it (as always, sorry), but a psychologist once cited a study that the vast majority of women are turned off by bodybuilding types - the huge big muscles, and for a good reason: for a man to look like that - as opposed to simply do modest fitness training which leaves you lean not pot-bellied, but not huge biceps - means that he invests a lot of time and energy in himself. That means either that he is insecure psychologically and has issues, which is not attractive in a mate; and/or that he values himself and his needs over the needs of the potential mate.
In other words, a guy who spends 4 hrs every day at the gym and eats protein shakes to bulk up, is an unattractive partner compared to a lean guy who goes biking or swimming for 30 min. 3 times a week (and those can be shared with a female) and eats healthy without being obsessive about it, because the latter has much more time to spend with and care for the female.
Personally, I agree completly. Also aesthetically: a bodybuilder pumped is unnaturally and looks therefore ugly. Take a look at the Greek statues that the greeks considered the height of beauty - from guys who regularly went to the gym to work out and keep fit (and fought a battle or war or competition regularly - they had to be fit!), and they look ordinary compared to a body-builder. But all that modest bicep served its purpose of hurling discus and throwing spears and carrying a shield while hacking a sword. They were not puny, they were well-proportioned.
Also, muscles alone are useless if you don’t have endurance - from aerobic exercise, like 30 min. biking or jogging. That’s what more important for your health, and will help to get rid of beer guts or similar problems, by burning the fat.
That may be true if you’re comparing a lean, muscular swimmer to a Schwarzenegger-style bodybuilder, but that’s not what most guys are trying to achieve. Most guys are trying to look more like this guy or this guy. Getting those kinds of physiques takes months of grueling work, including hours in the gym, but I haven’t heard any girls say they don’t like them because of that! 
You hear people say this quite a lot, but as comforting as it might be to think, “I don’t need to go to the gym, girls don’t like it anyway”, it’s clearly not true unless you’re talking about the extreme gym freaks.
Not only that, but the whole idea of a subconscious “He spends too much time on himself to be a good partner” rationale, suggested in constanze’s post, is far too neat and simplistic. If women don’t like guys with excessively muscular bodies, i think it has far more to do with simple aesthetics than with some deep-seated subconscious desire for an attentive mate.
It’s also worth noting, i think, that a lot of people don’t even realize the amount of time and effort it takes to make noticeable muscle gains. Perhaps one of the most interesting indicators of this is the comment that you hear sometimes, from both men and women (although more often the latter), along the lines of “I don’t want to work out with weights, because i don’t want to bulk up too much. I don’t want to get too muscular.”
The way some of these people talk, it seems like they believe that you can go to the gym a few times, lift a few weights, and your muscles will suddenly expand overnight and rip open the sleeves on your shirts.
News flash: you won’t just wake up one morning looking like the Hulk. Putting on any visible muscle at all takes time and effort, and bulking up a lot takes months.
Girls say that all the time, right? Would save me a lot of effort if that was how it worked. 
It’s also a bit counter-productive because coupling aerobic work with light resistance training would produce better results for girls who want to get the toned beach body than the aerobic work alone.
Well that makes some sense but why would lifting greater volume (more sets, somewhat more reps/sets) with less rest (classic hypertrophy training) result in less neuromuscular coordination than lifting lesser volume (fewer sets, slightly fewer reps/set) with more rest?
Great Philosopher, having those abs (and that’s what stands out in those pictures) also takes having hardly any body fat. A percent so low that few can sustain it, let alone sustain that low of a body fat percentage while keeping up that much muscle mass. Crunches won’t give abs like those. The stripped 5x5 won’t do it either. Liposuction maybe. I’d guess the most of the guys who maintain abs like that using those abs professionally.
You use more weight in the second program.
I second the recommendation for Starting Strength. It gets rave reviews from everyone who matters in fitness. I will be starting the program myself, shortly. Crossfit and P90X are two other well-known, much recommended programs. Incidentally both promote a diet similar to my own for best results.
Admittedly, there isn’t solid research into the effect on most people from eating how I am - grain and sugar-free, all whole unprocessed foods (animal products/veg/fruits), 200g natural fats per day, 100g protein (roughly a pound per body weight as I need to gain weight), 50-100g carbs. It’s vastly different from the diet of the normal American, and different even from the diet of most people who are actively trying to build muscle and increase performance. Sadly, athletes are told they ‘need’ to base their diet on simple carbohydrates. Vegetarianism is encouraged for anyone who’s health conscious.
But my results are entirely typical for people who are following the same plan - as per their statements and pictures, since we don’t have studies to back it up. Many of them get into it for fat loss, which it is excellent for, and end up with impressive gains in muscle mass and strength (and in general health as well). I don’t have fat to lose, and I’ve only put on about 5 lbs total. I’ve just gotten better (visible) muscle tone and more strength. 1 year ago, while I was around the same weight, I didn’t have ‘ripped’ (for a woman) abs. Today I do, without a single crunch (I do live an active life including some laborious activites, but don’t ‘work out’). I’ve also cured various health issues including some menstrual irregularites - and due to the ‘balancing’ of my hormones, I’ve put on some fat in just the right places (upper hips and boobs).
Take it or leave it, but I’m not the only one this works for. The ‘primal’ or paleo-style diet/lifestyle community is really taking off. A main reason is because it makes your body look incredible, without much effort compared to the more conventional methods of fat loss and muscle/strength gain.
Finally I found the prior thread I was referring to:
Ladies, Which Male Physique Do You Prefer?