Is fat loss different from fat burn? Dr. Layne Norton explains that fat burn is often misunderstood and mistakenly equated with losing body fat.
While fat burn plays a role in fat loss, it’s not the same as reducing overall body fat. What does it take to lose body fat? It begins with understanding the body’s fat balance and how it works.
Body Fat Balance
Body fat gain or loss depends on the balance between fat storage and fat burn, known as fat oxidation. Dr. Norton explains that you gain body fat when you store fat faster than you burn it. Your body fat remains unchanged if the storing and burning fat rates are equal. However, you lose body fat when you burn fat more than you store it.
This process isn’t as simple as flipping an on-off switch. The body’s metabolism is complex. Some functions may slow down or speed up but rarely stop entirely. These shifts in metabolic activity are influenced by hormonal changes and the availability of specific molecules in the bloodstream and cells, which regulate the relative rates of fat storage and burning.
[Related: Gene-Environment Interaction Explained]
Low-Carb Diet
Many individuals following low-carb diets or practicing intermittent fasting may claim fat oxidation and burning boosts. According to Dr. Norton, low-carb diets can lead to increased fat burn.
Consuming fewer carbohydrates reduces insulin levels, allowing the body to rely more on fat as an energy source.
Insulin can inhibit lipolysis, which is part of the fat-burning process.
—Dr. Layne Norton
A diet high in carbs can hinder fat oxidation. When you consume carbohydrates, the body stores a limited amount of glycogen and burns the excess through oxidation, leaving less opportunity for fat to be used as energy.
“If you’re oxidizing more carbohydrates, you’re oxidizing less fat,” Norton said. A high-carb diet results in reduced fat burning. However, it’s crucial to maintain a balance between the fat your body stores and the fat it burns.
High-Carb Diet
A high-carb, low-fat diet burns less fat but significantly reduces fat storage. Dr. Norton references a metabolic tracer study in which researchers tracked the carbon sources in fat cells. The findings revealed that less than 2% of stored fat came from carbohydrates, while over 98% originated from dietary fat. (1)
According to Dr. Norton, consuming more fat while reducing carbs and lowering insulin levels may lead to burning more fat and storing more fat. Ultimately, energy expenditure is key to determining body fat gain or loss.
“Are you eating more calories than you’re burning, or vice versa?” Dr. Norton said. A meta-analysis comparing high- and low-carb diets with equal protein and calorie intake shows no difference in fat loss. However, there is a slight preference for low-fat diets. (2)
Intermittent Fasting
Alternate-day fasting is effective in fat burning, depending on calorie balance. In a study exploring extreme intermittent fasting, also called alternate-day fasting, researchers compared alternate-day fasting to a consistent daily calorie intake.
One group consumed 75% of their maintenance calories each day, while the other alternated between consuming 150% of their maintenance calories on one day and fasting completely the next.
Results showed that fat oxidation rates were higher during fasting than those consistently eating 75% of their maintenance calories. However, on the days the alternate-day fasting group consumed 150% of their maintenance calories, fat oxidation decreased, and fat storage increased. Over the week, the total calorie balance evened out, explaining why no significant differences in fat loss were observed between the groups.
Intermittent fasting can be an effective tool for many people to manage overall calorie intake. Low-carb diets are often more sustainable for long-term adherence than low-fat diets.
Similarly, ketogenic diets, while more restrictive, can work well for those who find them easy to maintain. The key is selecting a consistent and sustainable dietary approach. At their core, these strategies are tools to achieve a calorie deficit essential for fat loss.
References
- Schwarz, J. M., Neese, R. A., Turner, S., Dare, D., & Hellerstein, M. K. (1995). Short-term alterations in carbohydrate energy intake in humans. Striking effects on hepatic glucose production, de novo lipogenesis, lipolysis, and whole-body fuel selection. The Journal of clinical investigation, 96(6), 2735–2743. https://doi.org/10.1172/JCI118342
- Hall, K. D., & Guo, J. (2017). Obesity Energetics: Body Weight Regulation and the Effects of Diet Composition. Gastroenterology, 152(7), 1718–1727.e3. https://doi.org/10.1053/j.gastro.2017.01.052
Featured image via Shutterstock/Kaspars Grinvalds
