How about some diet tips from the early 20th century? The Week has some excerpts from various books on the subject of dieting and nutrition. Most of them basically tell you to exercise, go outside, and don't eat so much. But then there's some weird advice from Helen Follett Jameson in her 1899 book The Woman Beautiful.
Do not drink much water. A little lemon juice added to it will make it less fattening.
There's this from Countess C, in the 1901 book Beauty's Aids: Or, How to Be Beautiful.
First and most important, drink very little, as little as possible, and only red or white wine, preferably Burgundy, or tea or coffee slightly alcoholized.
And from the 1892 book Beauty, Its Attainment and Preservation:
In America the number of fat people is growing larger every year and the suffering endured by this usually good-natured class of people is tremendous. As a matter of fact, a great deal of this discomfort might be avoided if people would not drink such an inordinate quantity of ice water and could be made to understand that thirst does not lie in the stomach and that it is not satisfied by pouring down water by the glassful.
The theory of water being fattening makes you wonder how much of what we "know" today will be laughed at in another 100 years. Read lots more at The Week.