Updated: 01/15/2018

Fit For Life Review - 5 Things You Need to Know


This review is what happened after I obsessed for weeks over Fit for Life. We took the time to create a comprehensive review, focusing closely on the ingredients, side effects, customer-service quality and scientific studies. After that we reviewed at numerous user comments from all over the internet. Finally, we summarized all of the pertinent data to give you the facts.

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What is Fit for Life?

The first thing you need to know is that Fit for Life is a diet program and best-selling book. The premise is that by eating more of the right kinds of food you can lose weight, change your life, and improve your figure without ever counting calories. It involves food combinations and timing meals to work with one’s natural body cycles. It also shares the menus, shopping lists, and exercise to follow for four weeks.

Fit for Life was written by Harvey and Marilyn Diamond. The book was originally published in 1985 and was followed by several companion books over the years. Although Mr. Diamond claimed to have a PhD, many academic and medical organizations have called his expertise into question. The school he received his degree from is not accredited. A revised edition was released in 2010, but read on…

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Lack of Evidence– “The Authors Aren’t Nutritional Experts”

Our first concern is that the authors of the Fit for Life book have no background in nutrition. Further complicating the issue is that the education they do have has been called into question. According to our Research Editor, “For someone to claim expertise in a topic when they do not have the training, studies, or personal experience to back it up is dishonest.”

One unhappy customer said, “I read this book over 10 years ago when I was more impressionable and less knowledgeable about health, fitness, and nutrition. Boy was I hooked…but the couple that wrote this book are not doctors and the whole book is based on very questionable theories.”

Another explained, “People lose weight on this program because they eat massive amounts of water based food and limit the high calorie concentrated foods. However, their premises and reasoning behind the entire Fit for Life program is false.”

Others were more understanding. According to one successful dieter, “The Diamonds have a few good notions but they appear to be directed by luck not scientific judgement. I still lost weight but not because of sound scientific judgement.”

One happy consumer said, “I have now kept the weight off for twelve years and I attribute it to the fact that this book is about a lifestyle change and not just a diet.”

Conflicting Science– “It’s Outdated”

One of the more significant concerns with the Fit for Life diet is that respected medical organizations such as the American Academy of Family Physicians and the American Dietetic Association list this as nothing more than a fad.

One reviewer put it simply, “This is a strange diet with no science behind it.”

Another was less generous and said, “A pseudo-science to sell books that is not based in fact. The book is so inane that it’s hard to believe so many people are falling for it.”

Other dieters felt they gained valuable insight from the book. One explained, “It is a great overview on proper eating and how the digestive system works.”

Another claimed, “One of the suggestions I got out of this book was to eat my fruits first thing in the morning and to only have fruits until lunch. This alone has changed my life.”

According to our research, a lack of evidence when combined with conflicting information from reputable scientific sources is a serious red flag. If the Fit for Life diet plan is out of touch with current trends, that’s not a good thing.

The Science – “Lacking Scientific Support”

At DietSpotlight, it is very important to us that any dietary plan be based on reliable scientific evidence. A person’s health and well-being is directly linked to their choices and basing those on unverifiable data has the potential to be negative. Fit for Life may offer some solid advice, but nothing that the dieter can’t find on the internet for free and some has even been rendered inaccurate over time.

The Bottom Line – Does Fit for Life Work?

What’s the real deal with the Fit for Life diet? The program has numerous glowing reviews from people who have successfully lost weight using the book. However, the science indicates that these individuals lost weight due to calorie restrictions rather than through any valuable insights from the authors. According to authorities in the field of health and nutrition, this is little more than a fad which is why we have reservations about giving it our support.

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Fit For Life

What is the Fit For Life diet?

The Fit For Life Diet is a series of books that point to healthy eating practices, such as, eating mainly living and high-water-content foods, having fruit all by itself for breakfast, and not mixing animal proteins with complex carbohydrates when eating them. The series is marketed by Marilyn and Harvey Diamond, which are two American authors. They both maintain that staying fit for life is easy if you follow seven specific habits, which include not depriving yourself, not making excuses, walking more, choosing activities that make you move, making your workouts shorter, discovering ways of making your vegetables more enjoyable, and making sleep a top priority in your life.

What are the ingredients in the Fit for Life Diet?

The ingredients for the Fit for Life Diet is fruit for breakfast. Animal proteins must not be consumed in conjunction with complex carbohydrates. Meat is limited. One is instructed to eat live food instead of dead food. Dead food is said to be food cooked to over a certain temperature, usually over 108 degrees. One should not eat foods from a can. White bread is not allowed. Vinegar in salad dressing is not allowed. Raw onions and garlic must be limited. Limit carbohydrates.

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What are the side effects of the Fit for Life Diet?

The side effects of the Fit for Life Diet can be summed up in the side effects that the food modifications required by the diet may cause. Examples of these side effects may include Vitamin B12 deficiency due to one limiting animal proteins via the diet. Low energy may be experienced from the limited carbohydrates.

Does the Fit for Life Diet work?

The Fit for Life Diet does work. The diet may not be for everyone as with most things, yet the Fit for Life Diet does work for some. There is a solution for every person.

What is the price of the Fit for Life Diet?

A new copy of The Fit for Life book written by the authors Harvey Diamond and Marilyn Diamond can currently be purchased for $13.04. The book that guides you through the Fit for Life Diet can also be purchased used for $1.33.

Where can I buy the Fit for Life Diet?

The Fit for Life Diet book can be purchased at Amazon.com and at BN.com. Simply do a search on each website for Fit for Life.

How should I take the Fit for Life Diet?

One should take the Fit for Life Diet slowly. This will allow the body to adjust to the changes in the variations of food consumption recommended by the diet.

How do I contact the Fit for Life Diet customer service?

While direct contact can only be made via the book, one can always search Youtube.com for Harvey Diamond and Marilyn Diamond. This will bring up more in-depth information and opinions on the diet.

Can I return the Fit for Life Diet book?

Yes the Fit for Life Diet book can be returned yet the information that you receive can literally change your life if the information obtained is applied.

What are the most common complaints about the Fit for Life Diet?

The most complaints about the diet are by far the deficiency of Vitamin B-12 in the body which means dips in energy. Other minor complaints are meal preparations for busy people due to the limited combinations of foods that are allowed. The most minor complaint is finding a location to eat out at restaurants again due to the food combinations allowed by the diet. All of the complaints are said to be minor due to the good results that the diet provides.


Previous Fit For Life Review (Updated December 12, 2012):

What You Should Know

Fit For Life is a book which takes a unique approach towards healthy eating written by Harvey and Marilyn Diamond and released in 1985. The premise of Fit For Life is that you can only lose weight and maintain a healthy body if you make long-term changes to your diet and that short-term dieting accomplishes nothing. Fit For Life became a best-seller and was followed up with Fit For Life II (1989), Fit For Life: A New Beginning (2001) and Living Without Pain: Fit For Life (2007). According to the Diamonds' website and all books in the series have sold over 12 million copies altogether. The recommendations in the book were unusual and although wildly popular on the talk show circuit were generally panned by professionals. But in the past twenty years many of Fit For Life's recommendations are being backed up by science and are in vogue.

Product Features

Fit For Life contained some unusual dietary recommendations including eating nothing but fruit before noon and not combining proteins with complex carbohydrates. In fact, food combining was a large part of the Fit For Life mantra; it isn't always what we eat, it's how we eat it. Fit For Life was also an early proponent of the raw food diet, postulating that we gain more nutrients from food that has not been cooked or processed. Fit For Life was also very militant in its view that hydrogenated fat was unhealthy. This philosophy has since proven as the medical industry now recommends natural oils and fats over hydrogenated oils. Anyone thinking of following the Fit For Life dietary lifestyle should check with their doctor or nutritionist to ensure that there is nothing in it that has since been scientifically proven to be harmful.


  • Promotes whole foods and healthy dietary lifestyle.
  • Recommends exercise.
  • Doesn't require purchase of expensive pre-packaged foods.


  • Not developed by trained medical or dietary professionals.
  • Some principles conflict with current belief about the causes of excess weight.
  • Has the potential to lead readers to believe that any ailment can be cured with diet and this may prevent some from seeking medical treatment.


The Fit For Life phenomenon has died down significantly from its hey day in the mid-'80's. However, the book still sells over 100,000 copies per year so many are still following its principles. There does not appear to be anything inherently unhealthy or dangerous about following the Fit For Life guidelines but we recommend that you consult your doctor or dietitian before starting.
Summer Banks Dietspotlight Author
About the Author:

Summer Banks, Director of Content at Dietspotlight, has researched over 5000 weight-loss programs, pills, shakes and diet plans. Previously, she managed 15 supplement brands, worked with doctors specializing in weight loss and completed coursework in nutrition at Stanford University. full bio.

38 Fit For Life Reviews

  • what about beans and rice

    They dont talk about eating beans..what about beans and rice?

    • Hillary

      Beans and rice is allowed see the chapter on food combining principle.

    • Maribel (Editor)

      Hi Gretchen! For detailed product and usage instructions, please refer to the Fit For Life official website for more information.

  • Yvonne

    I just wonder how the fruits consumed until lunch affect your blood sugar level? Usually doctors tell you not to eat too much fruit if you are hypoglycaemic or even diabetic.

    • Maribel (Editor)

      Hi Yvonne! Please make sure to consult with your physician before starting a new weight-loss program.

  • How this affects diabetes ?

    How does this diet affect diabetes. I’m border line diabetic and would like to reverse my condition by losing weight and eating properly.

    • Cameron (Editor)

      We like that this diet promotes a healthy lifestyle. A healthy low calorie diet will get you on the right track.

  • Can have water and fruit in morning?
    Mike McTamney (Verified User)

    Can you drink water during the morning hours you are suppose to eat only fruit?

    • Carol Elliott

      Yes, you can drink water. This diet is great and I was very successful in losing weight when this diet came on the scene. It is expensive with purchasing all the fresh veggies and fruits but will add years to your life and will gain loads of energy.

    • Maribel (Editor)

      Hi Mike! For detailed instructions, please refer to the Fit For Life official website for more information.

  • Your NameSREEKUMAR


    • Adrian (Editor)

      Hi! For detailed product and usage instructions, please refer to the Fit For Life’s official website for more information.

  • Grace

    It has been 10 good and healthful years with Fit For Life. I, together with my family just followed the principles outlined. It is so basic, so much of the Common Sense and does not bring you to the rigidity of counting calorie intake. I am 53 and I am not taking any maintenance for any disease. Thanks to the Diamonds.

  • Tonya

    I have been following Fit For Life since my early 20s (I’m now in my late 40s). My weight has only increased minimally over this time (5kgs), due to normal body changes with age. I have always cheated a little by having milk in my coffee and a small tub of plain yoghurt (with a sprinkling of cinnamon and a tablespoon of nuts or seeds) for mid afternoon snack. I firmly believe that not combining protein and starch in a meal is the trick – on the occasions when I have done this, then I always feel tired and “heavy” after that cheat meal. I do stick to only fruit until noon, and drink water and herbal or green teas during that time too (water alone gets boring). It works for me, but every body is different, so find the eating lifestyle that suits you and run with it (so to speak) – good luck!

  •  Thank You Marilyn
    Maria A Rooney (Verified User)

    I read this book when it first came out and it is probably,for me,the best book on health I have ever read. Eating only fruit in the morning cured my stomach ulcer. I never connected what I ate and the consequences of constipation from all the bacteria built up. Fast forward at least 20 years and now the medical professionals are getting the connections but they use drugs. Before I read the book, I was going to medical doctors and they gave me medicine that perpetuated the ulcer by constipating me. It was a miracle in my life that this book came out when it did. Also the body clock works also. It is true. I have followed Marilyn a little bit and she has diverted some from the all vegetarian way of eating and kind if went to the other extreme of eating red meat. All is good but I will never forget their first book and the life change it brought me. I will thank them now.

  • Jaz

    im 13 and I have done the fit for life now for about 5-6 months and I’m not losing any weight I’m just putting more on (6 kg ) and I’m felling really hungry because there is very little protean in this diet I’m not sure if this just me but if someone knows the a answer to why this is happening could you please reply?

    • Adrian (Editor)

      Hi Jaz. Please make sure to consult with your physician before continuing this product to make sure its safe and effective for you to use.

    • Baylee

      Probably because at the age 13 your body weight is supposed to fluctuate like crazy. You gain weight and then get taller. Girly, go eat a cheeseburger.

    • Maria

      Please please please do not go on a diet this young. Your body is still changing.

  •  It works !
    janie ramirez (Verified User)

    my husband and I did this diet and it works

  • Harvey diamond loves you

    For any questions that you want to ask Harvey, if you are on facebook, type in “harvey diamond loves you”, and it will take you to his page. He always answers any questions.

    • Jeannie

      I am thinking about going on Fit for life diet. I don’t have to lose any weight but am looking for help with digesting my food and would like help with my mental clarity. Has anyone have benefited from following this diet in these areas? Thank you for you responding to answering my request to my question.

      • Sharon

        Yes, it’s main goal is to make suggestion easier on your body. I have IBS & heartburn, but when I follow the diet, those things go away.

  • Don't want to give up coffee
    Val (Verified User)

    Has anyone had luck adhering to the fruit in the morning but also having coffee? I lost weight in the 80’s by following it strictly, but can’t muster the motivation to give up my coffee. Other than that I love the diet. Any thoughts?

    • Val

      I wonder that too. I also wonder if I am losing weight due to the principles since I dry. It all day or if it is calorie reduction. Still fell good and do believe.

    • Anonymous

      Drink coffee on an empty stomach, wait about 45min. Then have fruit

  •  Felt great, had more energy
    Wayne McClendon (Verified User)

    To make a long story short,it works as advertised. In my younger years went from 180 to
    135 lbs in a few short months. Felt great, had more energy, and felt good about myself.

  • G'Nell De Lack

    How does fit for life diet affect diabetics?

    • Maribel (Editor)

      Hi G’Nell! Because of possible interactions with diabetes, please make sure to consult with your physician before taking this product.

    Edwin Rivera (Verified User)


  • Irrelevant Comment

    I’m looking for the Diamonds website. Who knows the adress?

  •  I lost about 70 lbs over 6 months
    Renee (Verified User)

    I first read Fit for Life in 1990 after putting on 80 lbs with my pregnancy and breast feeding. I started having extreme heart burn no matter what I ate. My chiropractor boyfriend gave me this book to read. I started immediately and lost about 70 lbs over 6 months. I immediately had more energy and needed less sleep. My mood improved and I was always happy and energetic. I even started running. Over, the years, I did not follow the diet so well but when things got out of control I started back on it. It always immediately works and I feel great. I am 46 and very healthy. No medications or concerns. I do mostly eat organic and not a lot of meat. Medical evidence or not, this has worked for me for 18 years.

    • Your Name

      i am steeling your story

  • Can have water and fruit in morning?
    Mike McTamney (Verified User)

    Can you drink water during the morning hours when you are eating only fruit? Not sure if this working – sorry for multiple questions that are the same.

    • Diane Marks

      I’ve had this book since the early 90’s, two years ago I started seriously and have lost 15kilos. I;ve never felt better in my life, so much energy–I even started jogging and I’m 59.But when you have your fruit in the morning I only have a cup of warm water with it, I have tried coffee or green tea but my stomach feels better with just the water,2 hours later I’ll have a green tea, I’m afraid cofee is now a thing of the past for me now, after being a good coffee drinker for years. I love the way I feel and I sleep so much better too.

  •  Dr. Siegel is better than it.
    Judy Stark (Verified User)

    I tried the Fit For Life Cookie Diet because it was cheaper than Dr. Siegel’s Cookie Diet. I loved the latter, but the former was cheaper and thought I’d give it a try. The Dr. Siegel’s cookies are wonderful. And you really felt like you were eating a cookie. And they worked just as stated. On the other hand, the Fit for Life cookies were pretty bad. I felt like I was eating flavored mud. I guess if you took really small bites and just swallowed instead of chewing, it might be okay. But, what’s the fun in that? I’m going back to Dr. Siegel’s Cookie Diet.

  •  I not only lost weight, but I got healthy
    Lynne Dufour (Verified User)

    I bought, read, and followed “Fit For Life”, back in the 80’s. It is funny to read, good and healthy to follow, and is true. I not only lost weight, but I got healthy. My mother followed it and her acid reflux went away. Both of us has energy and felt great. I am going to get back to the basics once again. I have to find my book.

    • Dave from California

      Fit For Life is the way to love your life!! My doctor was amazed at the complete turnaround of my health! Cholesterol, Blood Pressure is now normal. Sleep Apnea is now gone. 60 pounds of extra weight is also gone. Doctor told me to just keep doing what I’m doing. I wish I could convince all my friends to follow the recommendations in this book. It has given me my life back!!