For about 70 years, scientists have known that restricting how much laboratory rats eat, while at the same time maintaining their nutrition, extends significantly how long the unhappy rodents will live.

In the mid-1990s, Leonard Guarente, a molecular biologist at MIT, discovered a gene in yeast and worms (called SIR-2) that responds to caloric restriction by producing an enzyme that shuts down long stretches of DNA involved with metabolism and aging.

Today, a small number of people try to trigger the therapeutic benefits of SIR-2 by practicing caloric restriction with optimal nutrition, CRON, or more simply, CR.

But the holidays are traditionally the time for gastronomic overindulgence. We pine for turkey, gravy, and pies. What’s a poor CRONer to do? We asked two of them, April Smith and Michael Rae, what they ate for Christmas dinner. They generously offered not only their recipes – but also to test-drive their holiday meal, and take a few pictures of the results for our viewers [click here to see photos].

Like many CRONers, Michael and April want to dispel the most common perception about caloric restriction: that it makes people miserable. Lenny Guarente recently told us, “Most people who have tried the diet find it unpleasant. It makes them cold, it makes them hungry, they’re irritable.”

Not so, say April and Michael. April is 31 years old, and lives in Philadelphia, where she’s the director of organizing for the Pennsylvania Association of Staff Nurses and Allied Professionals. She has been practicing CR since spring 2004. Most days, she eats around 1,200 calories. “The short term benefits of CR have been incredible for me. I never get sick. I sleep much, much better, and have more energy. I feel great in my body,” she says. Smith adds: “I have also experienced some emotional effects that are harder to explain. I am a more easy-going person. Stress affects me much less than before, and I am more patient, less likely to become irritated or lose my temper.”

Michael is 35 years old and lives with in Philadelphia with April. He’s the research assistant to Aubrey de Grey, the British theoretical biologist who believes he has found a “cure” for aging (see “Do You Want to Live Forever?”). Ordinarily, Michael eats a little more than 1,800 calories. Michael is less sanguine about the possibilities of CR. “It’s clear from the research that, even under the most optimistic scenario, adult-onset CR at a manageable level can only grant another decade or two of healthy life over and above the 5 years or so to be gained by leading an unusually healthy lifestyle,” he says. For him, “CR [is] as a bridge into a future in which emerging biotech will ultimately allow for a greatly extended youth.”

Here’s Michael and April’s Christmas dinner. (All measurements are per person.)

Christmas Salad with Hazelnut-Nutmeg Dressing

20 g arugula: 5 calories

37 g red pepper, diced: 10 calories

Dressing:

1 teaspoon hazelnut oil: 80 calories

4 g hazelnuts: 26 calories

1 tablespoon balsamic vinegar: 8 calories

Nutmeg: 0 calories

Directions: Arrange the arugula on a salad plate. Decorate with red pepper. Drizzle with hazelnut oil, balsamic vinegar. Dust with nutmeg. Arrange hazelnuts on top.

Turkey Breast with Mushroom Gravy

128 g turkey breast, roasted, skin removed: 160 calories

Gravy:

1/4 cup nonfat, plain yogurt: 28 calories

Third of a cube of no-salt vegetable bouillon: 5 calories

18 grams frozen Asian mushrooms: 4.5 calories

1/4 cup water

Directions: Simmer the bouillon until broth is made in the water. Add mushrooms. Continue to simmer until much of the liquid has evaporated off. Remove from heat and stir in yogurt. Serve over turkey.

Cranberry Relish

47 g cranberries per serving: 23 calories

Water to cover cranberries: 0 calories

Splenda/sucralose to taste: 0 calories

Ginger powder to taste: 0 calories

1/4 lemon (including peel), minced: 0 calories

Directions: Boil the cranberries until they pop and most of the liquid has cooked off. Add lemon and Splenda/sucralose and ginger powder to taste. Should be tart but not overwhelming. Serve warm or chilled.

Cauliflower Mashed “Potatoes”

100 g cauliflower per person: 25 calories

2 tablespoons fat free sour cream per person: 25 calories

Garlic powder to taste: 0 calories

1 tsp flax oil: 80 calories

Directions: Steam the cauliflower until very soft. Mash in the sour cream. Season with garlic powder to taste. Drizzle with flax oil just before serving (after removing from heat.)

Jack Daniels Pumpkin

1 cup canned pumpkin per person: 80 calories

5 ml Jack Daniels per person: 15 calories

Splenda/sucralose to taste: 0 calories

Cinnamon: 0 calories

Half-salt : 0 calories

Directions: Mix the pumpkin and the Jack Daniels in a sauce pan. Bring to a low boil. Add a dash of half-salt, Splenda/sucralose and cinnamon to taste. Reduce heat and simmer for half an hour. Serve hot. Dust with cinnamon or nutmeg before serving if desired.

“Miss Tenacity’s” Ginger Ricotta Cheesecake

1/4 cup fat free ricotta: 45 calories

30 g (1/8 C) EggBeaters: 15 calories

1/2 T whole wheat flour: 12.5 calories

1/2 of a two-teaspoon packet of Splenda/sucralose: 0 calories

1/4 capful vanilla extract: 0 calories

1 scant teaspoon powdered ginger : 0 calories

Directions: Combine all ingredients, stirring until smooth. Pour into small Pyrex bowl sprayed with nonstick spray. Bake at 375 for 30 minutes, until top is lightly browned and puffy. Set dish out on a rack to cool.

CR Punch

3 oz pinot noir: 64 calories

1 cup Diet Cherry 7-Up (or diet cranberry ginger ale): 0 calories

Michael’s entire dinner was only 629 calories. Since his breakfast was 622, and his lunch was 592, his total calories for that day were 1,843, only a little higher than his average caloric intake of 1,787.

Yet these low calories are only a part of the story. Using Dr. Walford’s Interactive Diet Planner, Michael and April calculated their nutritional intake for the evening. Michael’s meal was rich in protein, low in unhealthy fats, and replete with vitamins and micronutrients. For instance, he ate 43 grams of protein, but only 1 gram of saturated fats. He also consumed 48 percent of his recommended daily allowance (RDA) of iron, 229 percent of Vitamin C, and 691 percent of Lysine, to cite just 3 of the 39 different measures of nutrition that Michael and April monitor.

April ate the same-sized serving of salad, gravy, cranberry, and cheesecake as Michael. However, she omitted the hazelnut oil from her salad, saving 40 calories; she ate half the amount of turkey, saving 80 calories; and she skipped the Jack Daniels pumpkin, saving 95 calories. But she was boozier than Michael: she drank six ounces of wine instead of three, adding 64 calories. All in all, her CR Christmas dinner was 479 calories. Since her breakfast was 260 calories, and her lunch 351, her daily total was 1,090 calories, quite a bit lower than her usual 1,200. (She was therefore considerably more virtuous than Michael.)

One Technology Review editor, reviewing the menu, remarked, “I’d rather die young than eat that for Christmas.” Nonetheless, both April and Michael insist their meal was neither small nor evil-tasting. Certainly, the pictures the couple sent us suggest that their holiday “feast” was sufficient – and happily prepared and consumed.