The nation’s fattest president loved steaks for breakfast. Then he went on a diet.

One of the most entertaining White House memoirs in history was written not by a president, but by a maid.

Her name was Elizabeth Jaffray.

From 1909 to 1926, Jaffray was the chief housekeeper for four presidents – William Howard Taft, Woodrow Wilson, Warren Harding and Calvin Coolidge – and in a book titled “Secrets of the White House,” Jaffray chronicled their personal triumphs, foibles and domestic lives.

The meatiest of her stories were about her meatiest boss – Taft, a man so profoundly rotund that after sending a telegram to the secretary of war about a horseback ride, the secretary replied, “Referring to your telegram … how is the horse?”

As housekeeper, in addition to cleaning up after presidents, Jaffray was also responsible for their food – not just what they ate for themselves, but also what they served to guests. Doing their grocery shopping gave Jaffray tremendous insight into presidential tastes and appetites.

At one end of the spectrum was Coolidge, her last boss.

Coolidge was a cheapskate who complained that the hams he was served were too large. He could eat just one slice. Also, according to the book “Real Life at the White House” by John and Claire Whitcomb, his breakfast consisted of four pecks of wheat. How he survived on that caloric intake is one of history’s great mysteries.

At the other end: Taft, who occupied the White House from 1909 to 1913. The nation’s 27th president – who later became chief justice of the United States – was Jaffray’s hungriest boss.

For him, Jaffray bought “butter by the tub, potatoes by the barrel, fruit and green vegetables by the crate,” she wrote.

Oh, and meat. A lot of meat.

Taft ate steak for breakfast.

“He wanted a thick, juicy twelve-ounce steak nearly every morning,” Jaffray wrote.

What about eggs?

“President Taft liked every sort of food with the single exception of eggs,” Jaffray wrote. “He really had few preferences but just naturally liked food – and lots of it.”

The president scarfed down his steak breakfast every day at precisely 8:30 a.m. following a doctor-prescribed workout in his bedroom with a personal trainer – a collision of routines that first lady Helen Taft found rather funny, according to Jaffray.

(For the record, the famous story of Taft getting stuck in a White House bathtub? That’s untrue.)

So let’s return to his eating habits. If you think Taft was just ahead of his time – going low-carb before the Atkins diet craze – you will be disappointed to learn that in addition to the steak, Jaffray reports that Taft’s breakfasts included “several pieces of toast,” and his “vast quantity of coffee” was supplemented with large helpings of cream and sugar.

Under Jaffray’s watch, Taft got bigger and bigger.

In a diary entry from 1911, the housekeeper notes Taft’s weight – 332 pounds – and that he was going on a diet, apparently at the advice of his doctor. Taft told her, “Things are in a sad state of affairs when a man can’t even call his gizzard his own.”

Taft, who died in 1930 from heart disease, was deflated, but only metaphorically.

A year later, Jaffray wrote this in her diary: “The president looks as if he actually weighs 400 pounds.”

Eventually, Taft ordered a reduction in steak sizes.

Instead of 12 ounces, he was served six.

“But somehow,” Jaffray wrote, “he really didn’t take off any great amount of weight while he was president.”

Shocking.