When it comes to managing weight, the old adage “calories in vs calories out” is commonly referenced. (See my previous post about why this is not the full story.) While calorie intake matters, the source of those calories is just as, if not more, important.
Think of it this way, a calorie is a unit of measurement, that is all. Just like a mile is a unit of measurement. If you walked a mile along a flat grassy path or walked a mile up a steep mountain path, you have moved one mile in either case, however that mile (that unit of measure) is going to feel very different to your body. Ask any ultra marathon runner, not all miles are created equal. The same goes for calories — one calorie of carbohydrate has very different effects on the body than one calorie of fat or one calorie of protein. Not all calories are created equal.
Different types of macronutrients — carbohydrates, proteins, and fats — affect your body and metabolism in distinct ways, especially when it comes to insulin, a hormone that plays a central role in weight gain and fat storage.
Insulin’s Role in Weight Gain
Insulin is a hormone produced by the pancreas, and its primary role is to regulate blood sugar (glucose) levels. After you eat a meal, particularly one high in carbohydrates, blood glucose levels rise. In response, your pancreas secretes insulin, which helps cells absorb glucose from the bloodstream for energy or storage. However, insulin is also considered a "growth hormone," meaning it promotes not just the uptake of glucose but also fat storage. High insulin levels signal the body to store excess glucose as fat, which can lead to weight gain over time.
When insulin levels are elevated consistently (often due to diets high in refined carbohydrates), your body becomes more efficient at storing fat, particularly in adipose tissue. This is why insulin resistance, a condition where cells become less responsive to insulin’s signals, is often linked to obesity and type 2 diabetes. Understanding the relationship between insulin and weight gain is crucial for making informed decisions about the types of calories you consume.
How Macronutrients Affect Insulin Levels
Let’s break down how the three types of macronutrients—carbohydrates, proteins, and fats—affect insulin and blood sugar differently:
Carbohydrates: Carbohydrates have the most significant impact on insulin levels. When you consume carbohydrates, especially simple sugars or refined grains, they are quickly broken down into glucose, causing a sharp increase in blood sugar. Your body knows that high blood sugar levels are dangerous to your health so, in response, your body releases a large amount of insulin to help lower these glucose levels. Excess glucose that is not used for immediate energy is stored in the liver and muscles as glycogen, and once those stores are full, it is converted into fat. Over time, consistently high carbohydrate intake leads to higher insulin levels, promoting fat storage and contributing to weight gain. Do't forget, we need exactly zero calories of carbohydrates to survive (see my blog post on starchy carbs to learn more).
Proteins: Proteins have a moderate effect on insulin levels. While protein consumption does lead to some insulin release, it’s generally much lower compared to carbohydrates. Importantly, protein is also essential for many processes in the body like muscle repair and maintenance, and it doesn’t lead to large spikes in blood sugar.
Fats: Dietary fats have the least impact on insulin. When you consume fat, it does not cause a significant increase in blood sugar, and therefore, insulin secretion is minimal. This is why high-fat, low-carbohydrate diets like the ketogenic diet are associated with lower insulin levels. By reducing insulin spikes, these diets help the body rely more on fat for energy rather than storing it, which can promote fat loss in the long term.
Quality of Calories Matters
While the quantity of calories you consume is important, the quality and source of those calories are just as vital. Different macronutrients have varying effects on your metabolism, insulin levels, and fat storage. Carbohydrates, especially in excess, stimulate more insulin production and are more likely to lead to fat gain compared to fats and proteins.
By understanding how insulin works and how macronutrients affect it, you can make better dietary choices that help you manage your weight more effectively. Rather than focusing solely on calorie counting, consider the type of calories you're eating and how they impact insulin—a key player in the body’s fat storage and energy management system. And remember, metabolism is dynamic and individual so what worked for your best friend's cousin's sister may not be what will work for you, your best friend, or her cousin.
If you would like help to better understand the ratio of macronutrients that is best for you and your personal health goals do reach out.
To wellness!
April
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