Not necessarily, no. The problem was one of training as much as anything else. Professional British soldiers were just better prepared for your standard field battle than most of their American equivalents. Starving doesn’t help, but it isn’t the only or even necessarily the dominant factor in battlefield success. However it certainly can play a part under some circumstances. A very long, rambly, digressiony example which will eventually work its way back to food…
When the world was young and I was a fresh-faced youngster, I was writing a college paper for an European Imperialism class on Mehmed Ali of Egypt and his interactions with the European powers in the 19th century. In the course of the readings I was doing I came across a description of Napoleon’s siege of Acre ( where his campaign bogged down ). The British historian describing it made a comment roughly along the lines of “…the stubborn valor of the common Turkish soldier, at his best at position warfare.” Huh, I thought - I wonder what that means? I was well aware of 18th-19th century British racialist notions of, for example, “martial classes” in India. So I thought it was perhaps it was some similiar vestige of old racial superstition embuing Turks with some phantom character when fighting on the defensive. Or just as likely it was a fancy way of saying an inferior fighting force performed better on the defensive, pretty much a universal truism.
But many years later I found out that said writer was absolutely, 100% correct. In the 18th and very early 19th century, Turkish troops were in fact the best when fighting defensively. Not just better on defense than offense relative to themselves, but better at it than contemporary European armies. This despite the fact that Ottoman armies are pretty much considered to have overall been in steady decline vs. European quality since ~1700 ( and especially after ~1750 ). The answer to this seemingly contradictory Ottoman effectiveness while on the defensive comes down to the structure, philosophy and culture of the Ottoman military at the time.
Experience has often demonstrated that 10,000 well-disciplined troops sufficed to vanquish 100,000 Muslims; but an army of 100,000 did not suffice to force 10,000 besieged Muslims.
- Mustapha Efendi Vasif, an 18th century Ottoman chronicler discussing the 1768-1774 war.
It is is beyond all human comprehension to grasp just how strongly these places are built, and just how obstinately the Turks defend them. As soon as one fortification is demolished they merely dig themselves another one. It is easier to deal with any conventional fortress and with any other army than with the Turks when they are defending a stronghold.
- Austrian Field Marshal Baron Ernst Gideon von Laudon at the end of his life and after a highly successful and over 50 year military career, which culminated in his capture of Belgrade in 1789.
By 1700 the old timariot system of feudal levies had largely broken down. It had been replaced in part by an expansion of the kapu kulu ( the standing army including the famed, but increasingly less dominating, janissaries ), but more prominently by a new short term levy-en-masse from the lands of a new class of regional warlord that had grown to dominate the ever more decentralized lands of the Ottoman state. These hastily levied troops came in a couple of categories. On the one hand you had semi-professional mercenaries like the Bosnians or the very ubiquitous Albanians who formed part of the armed retinue of every Ottoman warlord from Bulgaria to the gulf. On the other you had a much larger mass of untrained or barely trained peasant militia. The commonality between them was an utter lack of military discipline. The usually very green militia were at best semi-useful cannon fodder who had a tendency to bolt at the first opportunity - 18th century Ottoman armies bled deserters in huge numbers. Better quality semi-regular troops like the aformentioned Albanians and Bosnians were reknowned for their savagery, and at times their savage bravery, but never for their discipline or steadiness.
The Ottoman regulars really weren’t much better. They had become a praetorianized elite who frequently dominated the government rather than the other way around. Not only did they occasionally intervene to overthrow sultans, every new sultan came to power with a massive gift in cash to the jannissary corps. Individual valor was highly prized, such that soldiers received cash rewrds on the spot from commanders for collecting heads and similar personal feats of arms. On the other hand drill and military discipline was not - an Ottoman observer watching the field practice of Frederik the Great’s army remarked with genuine horror that the common Prussian soldiers were treated "…worse than slaves." It was considered a great innovation when formalized drill sessions at a frequency of twice a week was instituted in the 19th century. Discipline was basically binary - either there was none or on the rare occasion the offense was severe enough to get noticed, there was execution. Add to this that the regulars regarded the non-professional troops with total contempt and you had the making of a field army utterly lacking in disciplined cohesion.
As a result Ottoman field armies tended to perform poorly against the increasingly tightly disiplined and drilled European forces. The extremely brave Turkish regulars seeking glory and prizes would sometimes launch disorganized attacks without orders, the green militia levies would not infrequently collapse on solid contact, the mercenary irregulars might concentrate on looting the enemy camp. Even in victory the Ottoman armies were hard to control, often partially dissolving as they hurled themselves pellmell after their vanquished foes. One of the reasons for the success of the Ottoman campaign against the Austrians in 1738-39 was the ability of a victorious Ottoman commander showed in holding his unruly army together after an initial victory and making an orderly, disciplined advance - it was remarked upon as unusual.
However there was a flipside to the above. Ottoman regulars in particular, as highly respected members of society with never a shortage of recruits, enjoyed an extremely high esprit de corps. The emphasis on individual achievement meant valour was prized above all - Turkish soldiers were usually brave to a fault .Perhaps most important of all their very praetoranization, as well as long-standing Ottoman military philosophy that had always heavily emphasized logistics, meant they were extremely well equipped and supplied. Much better than contemporary European armies - if you had to be a common soldier in 18th century Europe the lax, well-supplied Ottoman army was by far the most comfortable. By contrast their primary opponent in the 18th century, the Russian army, was well-drilled, brutally disciplined, recruited by forced conscription from the lowest segments of the peasantry and serfs ( essentially a death sentence until the late 19th century - the term of service was life ) and by quite deliberate fiscal policy starved and shoddily equipped. Early 19th century Ottoman troops on the march referred to their after meal leavings as ‘…fit only for dogs and Russians.’ Hard as taking Ottoman strongpoints were in terms of casualties, their fall meant huge stores of captured food, arms and ammunition for the perennially miserable Russian army.
Now at times oversupply could be a problem. At Zenta in 1697 the very size of the Ottoman supply train badly hampered the Ottoman ability to rapidly respond to Eugene of Savoy’s superbly timed ambush and probably cost them the battle.
But in defensive situations all the Ottoman weaknesses were nullified or greatly reduced and their strengths multiplied. Well-fed, lavishly supplied, fanatically brave with excellent morale - meanwhile the lack of battlefield discipline and cohesion mostly eliminated by the static nature of the combat. Consequently European armies feared to assault major Ottoman fortresses and the Ottoman state quite sensibly concentrated heavily on maintaining lines of formidable fortifications, especially on the Danube. One of the reasons for the long series of long, grinding wars in the 18th and 19th centuries was that the Ottoman defensive posture automatically equaled very slow, extremely costly campaigns. Repeatedly when reading about these wars you come across descriptions of armies balking before Ottoman strongholds because they were regarded as too costly to take, failing to take them by assault or taking them but at an extremely bloody cost. The Ottoman system, as increasingly bankrupt ( including financially ) and decrepit as it was, was very good at exacting a high cost from its foes and preserving the state for many long decades after it had become obsolescent.
So there you go. A long, boring discourse on one situation where better fed troops can matter :).