You are what you eat, when you eat and what you eat when. So if you’re one of those people who eats any time – maybe all the time – the ideas of nutrient timing and meal timing might help you go from resembling a saggy sack of sugar to looking more svelte and zucchini-like.

Meal timing means eating more often (no, I do not mean every five minutes instead of every 10 minutes) and nutrient timing means eating the right thing at the right time (no, I’m not talking about a box of chocolate chip cookies after every cigarette).

Put those two concepts together, and you have a recipe to get fit – and stay that way.

“When you eat makes a difference, and what you eat makes a difference, too,” says Dr. John Ivy, chairman of the Department of Kinesiology and Health Education at the University of Texas.

Ivy, author of “The Performance Zone and Nutrient Timing,” has a scientifically proven key to building better bodies: Eat the right foods right after your workout.

“When you exercise hard, you deplete energy stores in the muscle and cause muscle breakdown,” Ivy says. “There’s protein breakdown and fuel breakdown, and it doesn’t just reverse itself right away. You want to reverse that situation as fast as possible so you can start the recovery process immediately.”

The 30 minutes after exercise is the prime time to restore your body’s glycogen – its main fuel – and rebuild muscle, he says. That potential drops after an hour and even more after two, so it’s critical to eat foods that contain both carbohydrates and protein no later than 45 minutes after you’re done exercising.

“The major benefit is that you’re going to be able to recover faster from the workout,” Ivy says. “And depending on what kind of exercise you’re doing, you can increase strength, muscle endurance and aerobic endurance by taking nutrients at the appropriate time.”

Studying up

In one study, two groups of rats did exactly the same amount of exercise and consumed exactly the same number of calories, but one group ate carbs and protein immediately after exercise and again four hours later, while the other group ate four hours after their workout and then again four hours after that.

After 10 weeks, Ivy says, the first group had 8 percent more muscle mass and 30 percent less fat.

A 12-week study of people 70 to 75 years old found that the carb-protein combo right after weight training increased muscle mass and strength, while a group that waited three hours to eat the same foods showed no improvement.

Timing matters, but so does eating or drinking the right stuff. A liquid supplement containing a 4-to-1 ratio of carbs to protein works well, but so does a peanut butter and jelly sandwich and a glass of milk, Ivy says.

Speaking of carbs, Ivy loves ’em. Among other things, they keep your blood sugar levels on an even keel, which fights fatigue and supplies the muscle energy you need to exercise harder longer.

“Just following a good basic diet and supplementing at the right time may not sound all that exciting, but solid scientific research says it works,” Ivy says.

Critic of concept

Nutrient timing and eating like an athlete are different from meal timing, which is being touted as a sure-fire way to shed pounds. It has its fans, but Dr. James Rippe isn’t one of them.

Rippe, a cardiologist who partnered with WeightWatchers to write “Weight Loss That Lasts – Break Through the 10 Big Diet Myths,” pooh-poohs the idea that eating at any particular time will help you lose weight.

“No one schedule is better than another,” Rippe says, citing research showing that meal patterns – one meal or many, noon or night – had no impact on weight loss.

But other research shows that when you eat might have an impact on what kind of weight you lose.

Eating more often burned more fat and retained more muscle in a group of dieting Japanese boxers. They all ate 1,200 calories a day, and at the end of two weeks, they’d all lost the same amount of weight. But those who ate twice a day lost more muscle and less fat than those who ate six times a day.

‘The 3-Hour Diet’

The first step: ditch the three-squares-a-day concept, Ivy says. That’s the same advice outlined by personal trainer Jorge Cruise, who has built a diet plan around the multiple-meal concept.

His book, “The 3-Hour Diet,” is the antithesis of the anti-carb attitude. Eat every three hours, Cruise advises, and eat pretty much anything – in moderation, of course.

His plan works like this: Eat within an hour of waking, eat every three hours, and stop eating three hours before bed. Eat the foods he recommends in the portions he recommends, and you’ll beat cravings and binges, preserve your lean muscle and get rid of that roll around your middle, Cruise says.

No deprivation, no starvation, no stagnation. Yow.

You’ll also be eating only about 1,450 calories a day – tweaked a bit for body size – which will create a calorie deficit big enough to burn off two pounds a week.

Ivy also recommends five to six meals a day made up of 25 percent protein, 45 percent to 50 percent carbs and 25 percent to 30 percent fat. His approach is a bit gentler than Cruise’s and would result in a loss of about a pound a week.

What you eat matters, of course. Dr. Edward Diethrich, founder of the Arizona Heart Institute and co-author of “Fill Up to Slim Down,” recommends foods that make you feel fuller longer, mainly complex carbs such as oatmeal, whole-grain bread, brown rice and plenty of fruits and veggies.

But whatever you do, don’t eat right before bed.