The 5-Factor Diet, by Hollywood celebrity personal trainer Harley Pasternak (Meredith Books) is one of the newer diet books to make the bestseller list.

Harley Pasternak, the author, has a University of Toronto master's degree in exercise physiology and nutritional sciences. He is also certified by the American College of Sports Medicine and the Canadian Society of Exercise Physiology.

Harley's first book, 5-Factor Fitness (Putnam, 2005) was a number one top seller in its category at Barnes & Noble and Amazon.com. His follow -up book, 5-Factor Diet (Meredith, 2006) has met with equal success.   

Pasternak has worked with a near endless list of celebrities including  Halle Berry, Alicia Keys, Kanye West, Eva Mendes, Mandy Moore, Orlando Bloom, Benjamin Bratt, Rachel Weisz and Jane Fonda.

This is supposed to be a simple, yet comprehensive, stand-alone nutritional program that gets quick and lasting results. Dieters are told they will lose weight, get fit and gain more energy following the       5-factor Diet and exercise plans. 

It's all about the number 5. Pasternak wants dieters to commit to five short workouts a week and follow a five-week diet made up of five meals a day. Each meal and snack must contain a food from each of the five food categories: a protein, a low or moderate glycemic carbohydrate, a fiber a healthy fat and a sugar-free beverage. Each recipe requires only five key ingredients and takes only five minutes to prep.

There are 25 "5-Factor Must-Have-Foods," which include egg whites, seafood, beans, vegetables, salsa, mustard, jerky, no-flour crackers, water and sugar-free juice.

Pasternak steers people away form all foods made with refined flour and  added sugar.

This diet is supposed to be based in lifestyle changes, rather than on fads. Pasternak does do a good job of emphasizing healthy foods, such as whole grains, low-fat dairy, lean meats, healthy fats and lots of fruits and vegetables.

There is little talk of portion control, one of the most important components of healthy weight loss. Some have concerns that the diet will be hard to stick with over the long term, despite a "cheat" day once a week.

"I don't see any real science behind the 5-Factor Diet-- no studies to show it works, plus it doesn't seem to address a major problem linked to obesity, which is emotional eating", say weight control psychologists.

The "five; in the 5-Factor Diet comes not only form the number of elements each meal should include- protein, complex carbohydrates, fiber, fat, and fluids - but form the recommended five meals a day, with recipes that contain no more than five ingredients, or take no more than five minutes of prep time and five minutes o cooking time.

There is also a five-day exercise plan, which- no surprise - consists of five exercises that are done for 5 minutes each. the exercise is a combination of cardio and strength training.

What sets this plan apart is that the recommended food choices have what' known as a "low glycemic index." The glycemic index is a method of rating foods according to their ability to affect blood sugar levels in the body after eating.

For many people, emotions - not a drop in insulin levels - trigger eating. For these people, controlling insulin is not going to mean much in terms of controlling how much they eat.  

A new study for Tufts University shows that what matters most in weight loss is cutting calories and that both foods high and low on the glycemic index have  pretty much the same effect.

In the study, conducted in conjunction with the National Institutes of Health, Tufts researchers compared a diet of high glycemic foods with one of low glycemic foods, looking for differences in weight loss as well as hunger and feelings of satiation or fullness.

The conclusion: "Participants on our pilot study achieved and maintained comparable weight loss after one year regardless of whether they were on a low glycemic load or a high glycemic load diet," wrote study researcher Susan Roberts, PhD, director of the U.S. Department of Agriculture Human Nutrition Research Centers Energy Metabolism Laboratory

While there is no shortage of celebrity testimonies in the book, among "real people" criticisms noted on book review sites was the inconvenience of eating five times a day - especially every three to four hours. Critics also noted that is can be difficult to gain access to the snacks and meals the plan recommends, particularly for people who work outside the home.

The book provides some recipes for foods that can be made at home and brought to work as you would any other lunchtime fare.

It's important to note that while some experts believe that staying on the plan for the recommended five weeks can help to lose weight, most agree that the real value may come from being able to master the plan's unspoken rules - smaller portions, fewer calories, and appetite control - for life.

5-Factor Meal Delivery

If you are in the Los Angeles area, and want some real VIP treatment, you can be added to the already star-studded list of 5-Factor clients. For pricing and details on the 5-Factor meal delivery program, email mealdelivery@5factordiet.com.

The Online Factor

Harley has taken his celebrity approved diet and turned in into an interactive and customized online program. Studies show that people who participate in online weight loss programs lose more weight than those who go it alone.

Cost is $5 per week, billed quarterly, with a $65 automatic charge for 13 weeks.

Minimum 5-week charge of $25, non-refundable.