If you had read literally the first line of the article, you would see that it discusses the 1948-1949 years of the blockade. The wikipedia article you're citing covers the 10 years after 1945, which includes those years. Even if the years didn't overlap, human nutritional needs obviously didn't double in 6 years.
Of course, if you had read the wikipedia article you would have seen these lines:
The Supreme Headquarters Allied Expeditionary Force initially set the ration scale for Germans at 11,000 kJ (2,600 kcal) per day... Once the occupation of Germany commenced, it proved impossible to deliver the intended levels of food...As a result, once supplies which had been stockpiled by the German government during the war ran out, the ration scales were reduced to 4,200–5,200 kJ (1,000–1,250 kcal) per day.
So they didn't set the number to 1000 out of a principled stances about nutritional needs, it was what they could manage actually deliver given the enormous logistical and infrastructure limitations of the blockade.
The LA city (not Red Cross) document is much the same. Again, you've failed to read literally the next line in a document because the Red Cross is cited with the proper figure immediately after the "1500 calorie" figure:
The Red Cross suggests 2,000 to 2,500 calories per person, per day.
