[Benjamin Franklin], Poor Richard, 1742. An almanack for the year of Christ 1742. . . By Richard Saunders, philom. Philadelphia: Printed and sold by B. Franklin,  A 741p
Here's what he recommends (thanks to AMDOCs for saving me from having to transcribe it myself):
"Eat and drink such an exact Quantity as the Constitution of thy Body allows of, in reference to the Services of the Mind.
They that study much, ought not to eat so much as those that work hard, their Digestion being not so good.
The exact Quantity and Quality being found out, is to be kept to constantly.
Excess in all other Things whatever, as well as in Meat and Drink, is also to be avoided.
Youth, Age, and Sick require a different Quantity.
And so do those of contrary Complexions; for that which is too much for a flegmatick Man, is not sufficient for a Cholerick.
The Measure of Food ought to be (as much as possibly may be) exactly proportionable to the Quality and Condition of the Stomach, because the Stomach digests it.
That Quantity that is sufficient, the Stomach can perfectly concoct and digest, and it sufficeth the due Nourishment of the Body.
A greater Quantity of some things may be eaten than of others, some being of lighter Digestion than others.
The Difficulty lies, in finding out an exact Measure; but eat for Necessity, not Pleasure, for Lust knows not where Necessity ends.
Wouldst thou enjoy a long Life, a healthy Body, and a vigorous Mind, and be acquainted also with the wonderful Works of God? labour in the first place to bring thy Appetite into Subjection to Reason.
Rules to find out a fit Measure of Meat and Drink.
If thou eatest so much as makes thee unfit for Study, or other Business, thou exceedest the due Measure.
If thou art dull and heavy after Meat, it's a sign thou hast exceeded the due Measure; for Meat and Drink ought to refresh the Body, and make it chearful, and not to dull and oppress it.
If thou findest these ill Symptoms, consider whether too much Meat, or too much Drink occasions it, or both, and abate by little and little, till thou findest the Inconveniency removed.
Keep out of the Sight of Feasts and Banquets as much as may be; for 'tis more difficult to refrain good Cheer, when it's present, than from the Desire of it when it is away; the like you may observe in the Objects of all the other Senses.
If a Man casually exceeds, let him fast the next Meal, and all may be well again, provided it be not too often done; as if he exceed at Dinner, let him refrain a Supper, &c.
A temperate Diet frees from Diseases; such are seldom ill, but if they are surprised with Sickness, they bear it better, and recover sooner; for most Distempers have their Original from Repletion.
Use now and then a little Exercise a quarter of an Hour before Meals, as to swing a Weight, or swing your Arms about with a small Weight in each Hand; to leap, or the like, for that stirs the Muscles of the Breast.
A temperate Diet arms the Body against all external Accidents; so that they are not so easily hurt by Heat, Cold or Labour; if they at any time should be prejudiced, they are more easily cured, either of Wounds, Dislocations or Bruises.
But when malignant Fevers are rife in the Country or City where thou dwelst, 'tis adviseable to eat and drink more freely, by Way of Prevention; for those are Diseases that are not caused by Repletion, and seldom attack Full-feeders.
A sober Diet makes a Man die without Pain; it maintains the Senses in Vigour; it mitigates the Violence of Passions and Affections.
It preserves the Memory, it helps the Understanding, it allays the Heat of Lust; it brings a Man to a Consideration of his latter End; it makes the Body a fit Tabernacle for the Lord to dwell in; which makes us happy in this World, and eternally happy in the World to come, through Jesus Christ our Lord and Saviour."It's striking how much of this is still valid today. Of course, we no longer worry about our humor type, such as phlegmatic or choleric, when going on a diet, but such advice as bringing one's appetitite into subjection by reason, avoiding opportunities of temptation like "feasts and banquets," and taking a bit of exercise by "swinging a weight" is timeless. Not that it necessarily makes it easier to follow.
Of course, if you prefer a more 21st-century approach to resoltuions, here's Mashable's list of iPhone apps to help you keep your promises.
Happy New Year!