Fat Loss Guide: Understanding Fat Metabolism & Macronutrients

Fat loss has become important for all of us; whether we’re losing weight for our health, the beach, or a contest, we follow all kinds of diets and workout routines in an attempt to lose fat. Yet when people tell us what to eat, what workouts burn fat, etc; we fail to understand how fat metabolism works. This is strange considering that if you grasp an understanding for how fat is stored and utilized you will increase your chances of losing it and seeing the errors in a diet. The goal of this article will be to present you with facts on fat metabolism and dieting/exercise strategies to optimize fat loss while maintaining muscle mass.

Meal Timing

If you’ve read some of my articles previously than you are familiar with the reasoning behind having anywhere from 5-7 meals a day. This is not to speed up your metabolism but to provide proper insulin control. Insulin is responsible for pulling amino acids, glucose, and triglycerides from the blood and shuttling them where necessary. If your cells are active (working muscle, recovering muscle cells) they will be used for fuel; if they are dormant (adipose tissue), they will be stored as fat. Now to time your meals properly, you must understand the timing behind fat; triglyceride levels peak at about 4 hours after a meal, so your largest meal of the day should be early or around lunch time, and not late at night if your goal is to reduce body fat.

Knowing the timing behind insulin is important as well, insulin tends to remain elevated after a meal anywhere between 90 minutes to 4 hours after a meal, and so reducing carbohydrates up to 4 hours pre-exercise would be optimal. Exercising on an empty stomach or “starvation” cardio as it is called before breakfast in the morning is not recommended. Your body uses fuel based on what it can generate ATP (energy) with the fastest.

It begins with creatine phosphate, then glycogen, protein, then fat. Fat takes the longest to generate energy from (this is the reasoning behind low-intensity steady state cardio to use fat as a fuel source) but it provides the most ATP (it contains the most energy, which is why it is 9 calories per gram as opposed to 4 like carbohydrates or fat). So based on this, if you begin doing cardio while levels of glycogen (the storage form of carbohydrates in the body) are low, your body will begin to pull amino acids from muscle to use as fuel; only after this happens will your body begin to utilize fat.

Here are two sample macronutrient schedules based on morning training and evening training to maximize fat loss. The actual macronutrient amounts are relative based on weight and will be discussed later in this article. When zero carbohydrates are referenced, a lean animal meat source (fish, chicken breast, turkey breast) or protein powder is suggested. When low fat is being referenced, then it is best to only have your fats come from the meat in your protein source.

It is advantageous to utilize a low carbohydrate diet that employs more fats. However, for natural weightlifters the protein sparing and glycogen replenishing effects of carbohydrates are necessary to maintain muscle mass and the volume of exercise needed to burn the necessary amount of calories (1). Despite the abundance of calories contained in fat however, there is no conclusive research that shows a link between fat and improved performance.

Morning Workout:

  • Breakfast: protein, 0 carbs, low fat
  • Training and Cardio
  • Post-exercise: protein, carbohydrates, 0 fat
  • Lunch: protein, carbs, fat
  • Snack: protein, carbs, low fat
  • Dinner: protein, carbs, low fat
  • Bedtime snack: protein, 0 carbs, 0 fat

Evening Workout:

  • Breakfast: protein, carbs, low fat
  • Snack: protein, carbs, low fat
  • Lunch: protein, carbs, fat
  • Pre-exercise: protein, 0 carbs, low fat
  • Training and Cardio
  • Post-exercise: protein, carbohydrates, 0 fat
  • Bedtime snack: protein, 0 carbs, 0 fat

Total Macronutrients for the Day

As far as dividing up your total macronutrients for the day, a relatively higher carbohydrate, moderate protein, low fat diet is coming back into style for natural bodybuilders. To optimize fat loss, a low carbohydrate or carbohydrate cycling phase is still best when coming into the final weeks to optimize conditioning and take advantage of carbohydrate loading. However, continuing a low carbohydrate diet for extended periods of time for a natural lifter will almost always lead to large amounts of muscle wasting as your body will breakdown muscle for fuel.

Fat is still required in the diet to maintain healthy levels of testosterone and your dietary fat will come from your chicken, fish, and red meat once or twice a week. Natural bodybuilder Alex Stewart currently has a thread on his current progress with this style of dieting.

The reason having a higher ratio of carbohydrates is important when being involved in caloric restriction is that it can reduce oxidative stress and increase your lifespan (2). The reason this is important is because this is evidence that it is a diet that can be maintained for extended periods of time without the stress, fatigue, and cardiovascular damage of a high fat low carbohydrate diet.

Imagine if you were a natural bodybuilder preparing for a show, what would you prefer: 8-12 weeks of stressful low carbohydrate diet, or 12-16 weeks of a diet that provides you with plenty of energy, easy to find foods, and now stress until the final 4 weeks when carbohydrate cycling is incorporated. This macronutrient profile is especially effective for those who aren’t bodybuilders since finding low fat, carbohydrate foods and snacks are much easier than having low carbohydrate meals or snacks on the go.

Carbohydrates are proven for providing satiation and the feeling of fullness, however there is not enough evidence to prove that the high caloric count of fat provides the necessary feeling of fullness required for a diet (3). At 9 calories per gram it is too easy to overshoot the amount of calories you plan to provide yourself for the day, while at 4 calories per gram you could have almost twice as much carbohydrate. Any one who has been on a calorically restricted diet that incorporated fats outside of what was naturally occurring in their foods can attest to how hard it is to stop eating nuts, or to limit their scoops of peanut butter.

To calculate the number of calories to take in and the ratio of macronutrients, use a calorie calculator to determine the number of calories you require for maintenance and reduce that number by about 600 calories or by about 20%.

The diet itself will be broken up into 50% carbohydrates, 35% protein, and 15% fat. While dieting you will only need enough protein every 3 hours to maintain a positive nitrogen balance, the relatively high ratio of carbohydrates will spare muscle protein during caloric restriction and provide energy for your workouts. The timing of your carbohydrate intake will allow insulin levels to subside before your workout allowing for more fat utilization during the workout itself and the subsequent cardio.


A supplement that has much research to support it’s acute (short-term, usually 2 weeks or less) effectives are the Medium Chain Triglycerides. They are a form of fat this is broken down quickly and used readily as fuel. It was suspected that athletes with a higher fat utilization like long distance runners could benefit from supplementing with this fat but the results were inconclusive (4).

However, they are research proven to provide a thermogenic effect as a result of fat oxidation and increase fat utilization (5). This fits perfectly into the diet during the final weeks when you take advantage of the rapid, short term fat loss associated with low carbohydrate dieting. Because the effects last less than 2 weeks it is best used in conjunction with carbohydrate cycling during the low or no carbohydrate days as your supplementary fat.


The big picture for weight and fat loss is expending more calories than you take in. The instances in which this gets tricky is when muscle mass is low: where building muscle will be the focus; obesity: increasing work capacity will be the focus; and states of low metabolic rate from lengthy dieting: incorporating new strategies like cheat meals and increasing cardio are key. The best way to know what works, and to save yourself from having to try every type of diet; is to develop a better understanding for how fat works and how it’s metabolized. Then once you’ve got the timing, meal composition, and total calories down…the rest is just all about training and commitment.