Flexible Dieting : IIFYM

 By Mizpah Matus B.Hlth.Sc(Hons)

Flexible Dieting or If It Fits Your Macros (IIFYM) simply refers to a way of eating where you are less strict about your diet. Rather than following a rigid set of rules you will adopt a more relaxed approach to what you eat.

flexible dieting

Recently this dieting method has gained popularity as a revolutionary weight loss technique.

However, there isn’t one basic definition of what it means to follow a flexible diet. There are many different ways to undertake flexible dieting depending on your personal preferences and goals.

Flexible Diet Basics

When people follow a strict diet, at some stage they begin to feel deprived and start craving restricted foods. After weeks without indulging in their favorite meals, eventually they give in.

When this happens most people give up off their diet completely for a time and regain weight rapidly. After a several days or weeks they may return to the strict diet and repeat the cycle.

Conversely flexible dieters realize that an occasional treat – or eating something that is not usually “allowed” – is not a big deal. A little indulgence will not have a major impact on long-term weight loss results.

What is Flexible Dieting?

In general terms a flexible diet does not require you to follow a strict set of rules. You can enjoy your favorite foods to avoid feeling deprived and without experiencing guilt.

The main principles of flexible dieting include:

  • Dieters Calculate their Total Daily Energy Expenditure.
  • Establish macronutrient levels according to your goals.
  • Eat healthy foods that you enjoy.
  • Allow yourself to eat your favorite foods in If It Fits Your Macros.
  • Don’t feel guilty about eating something not “on” your diet.
  • Avoid classifying foods as “good” or “bad”.
  • Relax and continue with your diet if you do indulge or overeat.
  • Focus on sustainable long-term results instead of rapid weight loss.


iifym bookThere aren’t really any additional costs with flexible dieting unless dieters sign up for personalised coaching or programs.

A great option is the book, Flexible Dieting: Lose Weight and Start Eating Again, and contains everything you need to know and do to be successful with flexible dieting. Recipes, meal plans, calculations, and much more.

It retails for $19 and is available as an instant download.

Learn more here.

Flexible Diets Are More Effective

Research has shown that rigid dieters often weigh more and have less success over the long term than flexible dieters.

Flexible dieting may produce a slower rate of weight loss in the beginning. However, usually people experience better results over the long-term.

Method 1: Reducing Calories with Portion Control

In most cases a flexible diet for weight loss will be very similar to your regular diet. This allows for a smooth transition from your usual way of eating, which makes dieting a lot easier.

However if you are trying to lose fat you will need to reduce your intake of calories.

You don’t necessarily have to count calories. If you choose not to do so you could simply reduce portion sizes while continuing to eat the same foods.

Method 2: IIFM – Tracking Macronutrients

IIFYM Macros
Another approach to flexible dieting is referred to as “If It Fits Your Macros” or IIFYM. With this method you plan your meals and track your intake of macronutrients – protein, carbohydrate and fat.

This method can influence body composition more effectively than simply monitoring calorie intake. It can be applied to different goals including fat loss and lean muscle gain.

You will plan your daily meals to provide a certain number of grams of protein, carbohydrate, and fat each day. There are no good or bad foods as long as you keep within your designated macronutrient ratio.


  • Dieters can enjoy all of their favorite foods.
  • The diet is individualized to suit your personal preferences.
  • You are not required to eat any foods that you don’t like.
  • Research shows that flexible dieters have better long-term success.
  • You can enjoy an active social life without worrying about your diet.
  • Reduces the stress that is generally associated with strict diets.


  • May encourage some dieters to continue eating unhealthy foods.
  • Necessary to monitor calories, portion sizes or macronutrient intake.
  • Does not place attention on the potentially negative health effects of certain foods such as refined carbohydrates or trans fats.
  • Some dieters may have difficulty limiting their intake of certain foods to small portion sizes.
  • Weight loss may occur more slowly than on a structured diet.

Moderation is Key

Flexible diets are easier to follow and more enjoyable because they are based on your own food preferences. You can also continue to include your favorite treats in moderation.

However, to support your health it is best to consume the majority of your calories from the nutritious foods you enjoy. As long as most of your diet is healthy this can be an effective method for maintaining healthy weight loss.

Flexible Dieting Resources

  1. Flexible Dieting Basics at Evidencemag.com.
  2. Flexible Dieting Guide at HealthyEater.com
  3. IIFYM Guide at MuscleforLife.com
  4. MyFitnessPal: App for Tracking Calories/ Macros
  5. Free Tool for Figuring your Total Daily Energy Expenditure at Freedieting.com

  • Rolland-Cachera, M. F., Deheeger, M., Akrout, M., & Bellisle, F. (1995). Influence of macronutrients on adiposity development: a follow up study of nutrition and growth from 10 months to 8 years of age. International journal of obesity and related metabolic disorders: journal of the International Association for the Study of Obesity, 19(8), 573-578. abstract
  • Layman, D. K., Boileau, R. A., Erickson, D. J., Painter, J. E., Shiue, H., Sather, C., & Christou, D. D. (2003). A reduced ratio of dietary carbohydrate to protein improves body composition and blood lipid profiles during weight loss in adult women. The Journal of nutrition, 133(2), 411-417. abstract
  • Layman, D. K., Evans, E. M., Erickson, D., Seyler, J., Weber, J., Bagshaw, D., … & Kris-Etherton, P. (2009). A moderate-protein diet produces sustained weight loss and long-term changes in body composition and blood lipids in obese adults. The journal of nutrition, 139(3), 514-521. abstract
 By Mizpah Matus B.Hlth.Sc(Hons)
Last Reviewed: July 22, 2015. Disclaimer