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Flexible Dieting/ IIFYM Intro

Steps to start using the Flexible Diet/ Counting Macros/ If It Fits your Macros IIFYM

  1. Buy a digital food scale and weigh your food in grams, uncooked.

  2. Sign up to Log all of your food in grams, uncooked.

  3. Weigh everything you eat for the first 3 months. Eventually, you can eyeball it but we suggest staying consistent with the scale for best results.

  4. Log every single thing you eat at, no matter how small, or how “healthy” you think it is. If you eat it, track it!

  5. If dieting to burn fat and lose weight, eat between 15% – 20% calories less than your body needs. This is your TDEE (total daily energy expenditure). Calculate your TDEE with this TDEE Calculator. If you are trying to put on muscle mass and gain weight, eat between 5% and 10% more calories than your TDEE, every day (preferably from carbs).

  6. To dial in IIFYM with more accuracy, follow these steps:

    • Eat at least .8 grams of protein per pound of lean body weight (total body weight, less total fat weight).

    • Eat between .3 – .4 grams of fat per pound of lean body weight.

    • Any remaining calories you have left in your daily total will come from carbs.

    • Take in 20-25% of your lean body weight (in grams) in fiber every day (this should be included in your carbohydrate total).

    • Drink 3-4 liters of water per day in addition to any other liquid you consume.

    • The more consistent your sodium and water are, the more stable your weight will be. While important to many functions in the human body, sodium and water have very little relation to fat loss, but does have a large effect on water retention and body weight fluctuations. We mostly encourage sodium tracking so that it is easier to track your body weight, and thus make your adjustments based on more accurate information.

  7. Once your fat loss stalls, reduce your daily intake of carbs by 10-15 grams (people with more weight to lose can go higher than those with less to lose.) Adjust your macros ONLY when your fat loss stalls for 10 days or more. Never reduce calories, carbs, or fat if you are still making fat loss progress. Any changes you make should be few, infrequent, and deliberate.

  8. Things to remember:

    • Select foods that are rich in micronutrients (vitamins and mineral) first. Once your micronutrients are met, go for food that you enjoy eating, while staying within your personal range of macros. (Once micro-nutrients are met, worry less about the foods you eat, and more about the macros you meet).

    • Take a gender-specific multivitamin to ensure your micronutrients are being met.

What are Macronutrients (Macro)?

In the context of health and fitness, macronutrients are most often defined to be the chemical compounds that humans consume in large quantities that provide bulk energy. Specifically, they refer to carbohydrates, proteins, and fats. Some definitions also include water, air, calcium, sodium, chloride ions, and some other substances, along with more typical macronutrients, since they are needed in large quantities by the human body. In this calculator, we only calculate daily carbohydrate, protein, and fat needs.

Micronutrients are another essential part of human nutrition and consist of vitamins and dietary minerals such as Vitamin A, copper, iron, and iodine. While macronutrients are necessary daily in amounts on the order of grams, humans typically only need fewer than 100 milligrams of micronutrients each day.


Proteins are organic compounds comprised of amino acids, and are one of the types of macronutrients. Amino acids are essential to a person's well-being, and there are certain amino acids that can only be obtained through diet. These amino acids are typically referred to as "essential amino acids," and are obtained by humans and other animals through the consumption of protein.

There are numerous sources of protein, both animal (meat, dairy, etc.) and plant-based (beans, legumes, nuts, seeds, etc.). There also exist protein supplements that are sometimes used by people who are trying to build muscle. Although protein is a necessary part of the human diet, as with most things, moderation is important. There are also healthier and unhealthier proteins.

Healthier proteins include:

  • Soy

  • Beans

  • Nuts

  • Fish

  • Skinless poultry

  • Lean beef

  • Pork

  • Low-fat dairy products

Unhealthier proteins include:

  • Fried meats

  • Processed meats (deli meats, sausages, fast-food burgers etc.)

  • High sugar yogurts

  • Processed protein bars

  • Many kinds of cheese

Carbohydrates (Carbs)

Carbohydrates, often referred to as simply "carbs," are compounds that are typically classified as sugar, starch, or fiber. Sugar is the simplest form of carbohydrate, while starch and fiber are complex carbohydrates. Carbohydrates are often also classified based on the number of saccharides that comprise them: monosaccharides, disaccharides, oligosaccharides, and polysaccharides. Monosaccharides and disaccharides are often referred to as "simple carbohydrates," while oligosaccharides and polysaccharides are referred to as "complex carbohydrates."

Glucose is a monosaccharide and is one of the key sources of energy for humans, as well as other animals. Polysaccharides such as cellulose cannot be easily metabolized by many organisms, including humans, but can still provide them with valuable dietary fibers, which helps with digestion. Too many carbohydrates in the form of sugar (common in processed foods) can have negative health effects, but more complex carbohydrates (from vegetables, fruits, whole grains, legumes, etc.), particularly those that provide dietary fibers, are beneficial, and necessary for the human body.


Fats are molecules that are comprised primarily of carbon and hydrogen atoms. Common examples include cholesterol, phospholipids, and triglycerides. Although fats, in the context of nutrition, are typically viewed as unhealthy, they have both structural as well as metabolic functions, and are a necessary part of the human diet. They are also highly energy dense and are the most efficient form of energy storage.

Fats are typically classified based on the bonding of carbon atoms. In terms of dietary fats, the most commonly referenced fats include saturated fats, unsaturated fats, trans fats, monounsaturated fats, polyunsaturated fats, and omega-3 fatty acids. Generally, saturated and trans fats are considered unhealthy fats, while monounsaturated, polyunsaturated, and omega-3 fatty acids are considered to be healthier, better sources of fat for the body.

General recommendations from the Dietary Guidelines for Americans for 2015-2020 include entirely avoiding trans fats where possible, limiting saturated fat intake to comprise less than 10% of calories consumed per day, and ideally replacing saturated fats in the diet with monounsaturated and polyunsaturated fats.

Daily Calorie Needs

The number of calories a person needs to consume on a daily basis is mainly based on a number of factors including height, weight, age, and activity level, along with whether the person wants to maintain, lose, or gain weight. The values returned by the calculator are based on two equations for estimating the basal metabolic rate (BMR) or resting daily energy expenditure (RDEE) of a person. Once the BMR or RDEE is calculated, they are then multiplied by an activity factor to estimate daily caloric needs. The Mifflin-St Jeor Equation is a widely adopted equation that calculates BMR mainly based on physical characteristics such as body weight and height. The Katch-McArdle Formula calculates RDEE, which takes lean body mass into account. The Katch-McArdle Formula can be more accurate for people who are leaner and know their body fat percentage.

Based on the above factors, an average person may need to consume anywhere from 1600-3000 calories a day. The recommendations are generally higher for men (2000-3000) than women (1600-2400), and an increased activity level requires more calories, while a sedentary person would require less.

As carbohydrates, proteins, and fats provide nearly the entire energy needs of the human body, their daily needs can be calculated based on the daily caloric need. The values returned by the calculator are an estimate based on standards and guidelines provided by a number of institutions, such as the American Dietetic Association, Centers for Disease Control and Prevention, World Health Organization, and more

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