The weight problem has reached crises proportions within the U.S. Army infantry. No, not the weight of the troops. Infantry soldiers are rarely overweight. But they are carrying more and more weight, and it's having an adverse effect on performance, morale and physical fitness. Troops are frequently carrying 50-60 kg (110-132 pounds). That means they cannot move as fast as the enemy, and when they try to they tire faster and get frustrated, and often injured (by the enemy or by the sheer physical stress of hustling with all that weight on them.) Long term, troops are developing the kind of physical stress injuries athletes are prone to (eventually) when they overdo it.
The problem has been around for a long time, and the senior commanders, and the various procurement bureaucracies that supply essential equipment, have not been able to make the kind of effort that would solve the problem. The procurement bureaucrats all see their items as essential, and making them lighter is not a high priority. The brass insist on a lot of stuff being carried mainly so there will be no media blowback if someone, somewhere, complains that troops died because they lacked a particular item.
It's not that the army doesn't try. Two years ago, a battalion in Afghanistan was equipped with the lightest substitutes the army could find for body armor, packs, boots and other gear, while simply leaving some stuff out entirely. This resulted in 10 kg (about 22 pounds), depending on the mission, being removed from the soldiers combat load. The effectiveness of the battalion was monitored, along with the injury and casualty rates. The troops (including officers and NCOs) were interviewed, to get a better idea of just what happens, good and bad, when the weight is reduced. After all that, the brass saw the results and realized that they had a long way to go to get the load permanently reduced, a lot. The troops liked the lighter weight, but some of the brass and bureaucracies were not happy with the exposure (to accusations of "not doing enough for the troops.") A major, and real, effort to reduce the weight is still blocked by officers and officials more concerned with their careers and reputations than with the welfare of the troops.
The biggest, and heaviest, problem is body armor. Although the new armor offers better protection, it is heavier and bulkier, thus inducing fatigue and hindering mobility. This often led to battlefield situations where a less tired, and more agile, infantryman could have avoided injury. Military and political leaders usually do not appreciate this angle. But the troops do, as it is a matter of life and death for them.
Senior commanders are under a lot of pressure to keep friendly casualties down, so they tend to insist that the troops wear all their armor all the time. Despite this, some subordinate commanders look the other way when troops shed their armor temporarily to get some needed speed. The new protective vests now have a quick release feature, that makes it easier to get the vest off, and back on again.
Many soldiers and marines point out that the SOCOM operators (Special Forces and SEALs) will sometimes go into action without their protective vests. Again, that is done because completion of the mission is more important than covering your ass when a reporter goes after you for "unnecessary casualties." Many of the troops are willing to take the risk, because they believe, for example, that taking down a sniper when you have the chance, is worth it. If you don't catch the guy, he will be back in action the next day, killing Americans.
Currently, the lightest load carried, the "fighting load" for situations where the troops were sneaking up on the enemy and might be involved in hand-to-hand combat, is 28.6 kg (63 pounds). The "approach march load," for when infantry were moving up to a position where they would shed some weight to achieve their "fighting load", is 46 kg (102 pounds). The heaviest load, 60 kg (132 pounds), is the emergency approach march load, where troops had to move through terrain too difficult for vehicles. As in the past, the troops often ignored the rules and regulations and dumped gear so they could move, or keep moving.
In Afghanistan, the problem is made worse by the high altitudes (up to 5,000 meters) the troops often operate at. The researchers found that in Afghanistan, even though the infantry were in excellent physical shape, troops would sweat nearly 590 ml (20 ounces) of fluid an hour while marching at high altitudes in bright sunlight in moderate temperatures. That meant more weight, in water, had to be found to keep these guys going.
A lot of the weight carried is essential stuff. Weapons, for example. The Army saved about a kilogram (two pounds) in the 1960s when they switched from the M-14 rifle to the M-16. A lot of weight was saved in ammo carried as well, because a hundred M-16 bullets weighed two pounds less than a hundred 7.62mm M-14 ones. Troops usually carry 200-300 rounds of rife ammo with them. Plastic canteens replaced metal ones and lighter sleeping bags showed up, as well as lighter clothing. Lighter food (pouches of MREs instead of cans of C Rations). But heavier stuff was added, like the 7.7 kg (17 pound) "Interceptor" bullet proof vest and the heavier Kevlar helmet. Special Forces troops often go into action without body armor, and keep the load under 18 kg (40 pounds). But that's only in those situations where the Special Forces calculate that speed and achieving surprise are worth more than the protection the vests provide. Most troops do not have that option, but they do need less weight on their back to remain competitive with the enemy they fight in rural Afghanistan. With enough development effort (which is expensive), the weight problem could be solved. It also takes will and cooperation on the part of the senior commanders and procurement bureaucrats. Thus it's possible. But so far, it's not been done.