"Pick a color, basically, and only eat the food that's that color."
Sass remembered orange is a common color, because it includes a lot of foods: carrots, sweet potatoes, mangos, oranges, papaya. "People think, 'Ooh, I'm only eating all these healthy foods, but balance is essential for getting most bang for your buck, foodwise.
"Orange wouldn't be a bad color to pick. However, I can't think of any protein foods that are orange," said Sass, adding that while beta carotene in the orange food is healthy, people also need to eat fat to absorb it.
Another short-term diet Sass has seen people try before weddings or high school reunions is the one-item diet. The only rule is to eat the one dish, for example chicken soup, for breakfast, lunch and dinner. The premise is if you eat only one food, you'll be so sick of it that you won't overeat.
"This one woman picked soft pretzels," Sass said. "I think that woman picked those because she had a fat phobia and she knew they were low-fat."
As with the one-color diet, the one-food diet can have some unforeseen pitfalls. Without enough nutrients, Sass believes people will actually want to rest rather than go out and burn calories. "If you are only eating soup or pretzels -- you're just going to feel like crashing on the couch or going to bed early."
Sass has seen worse diets than the depressing life of soft pretzels. Sass really hates the ideas that play on people's shame -- the so-called bikini and mirror diets.
Both the bikini and the mirror diets aim to motivate, or shame, people into eating right by making them self-conscious. Dieters can eat what they like, but they must eat it in front of a mirror or while wearing a bikini.
"I would never recommend that somebody do something that's trying to shame them and make them feel bad," Sass said. "You're creating more negative emotions that may make you want to binge eat."
If mirror dieting is on the mental extreme of ill-conceived fitness ideas, Sass said the physical extreme would be the burn-it-all regimen.
"It's trying to burn the same number of calories that you eat during exercise," said Sass, adding that the math is not on the burn-it-all fitness regimen's side. Because most people burn 500 calories per hour of aerobic exercise, someone would have to exercise for three hours to burn the recommended 1,500 calories.
Like extreme diets, many nutritionists and doctors said lofty exercise hopes are actually a common source of fitness folly.
"Many of my patients try going from sedentary to extreme exertion to lose weight fast," said Dr. David L. Katz, director of the Prevention Research Center at Yale University School of Medicine and a medical contributor to ABC News.
"It generally results in injury and rapid burn-out, and no sustainable benefit," Katz said.
Ayoob also sees this as a problem, but more often, he calls it the weekend-warrior syndrome.
"This is not a race," Ayoob said. "Especially with the Olympics, stop trying to be Michael Phelps. I'd much rather see someone go on a 1-mile jog every day, than a 7-mile jog once a week."
Ayoob has a common recommendation for the all-or-nothing busy athlete: Do a pushup a day, and at the end of each week, add another pushup. "In six months, you'll be doing 26 a day and you'll be past where you need to be," he said.