Question

(a) Which releases the most energy when metabolized, 1 \(\mathrm{g}\) of carbohydrates or 1 \(\mathrm{g}\) of fat? (b) A particular chip snack food is composed of 12\(\%\) protein, 14\(\%\) fat, and the rest carbohydrate. What percentage of the calorie content of this food is fat? (c) How many grams of protein provide the same fuel value as 25 of fat?

Short answer

(a) 1g of fat releases more energy when metabolized compared to 1g of carbohydrates, with 9 kcal compared to 4 kcal, respectively. (b) About 26.81% of the calorie content of the chip snack food comes from fat. (c) Approximately 56.25g of protein is needed to provide the same fuel value as 25g of fat.

Step-by-step solution

(a) Comparing energy released by carbohydrates and fat

To determine which releases the most energy when metabolized, we first need to know the energy content of carbohydrates and fats. The energy content of carbohydrates is 4 kcal/g, and the energy content of fats is 9 kcal/g. Now, let's compare the two values: Carbohydrates: 1g × 4 kcal/g = 4 kcal Fat: 1g × 9 kcal/g = 9 kcal As we can see, 1g of fat releases 9 kcal, which is greater than the 4 kcal released by 1g of carbohydrates. So, 1g of fat releases more energy when metabolized compared to 1g of carbohydrates.

(b) Calculating the percentage of calorie content from fat

The chip snack food is composed of 12% protein, 14% fat, and the rest carbohydrate. We need to find the percentage of calorie content contributed by fat. We are given the percentage of each macronutrient by mass, so let's assume 100g of the snack food to make our calculations easier. Protein: 12g Fat: 14g Carbohydrate: 74g (100g - 12g - 14g) Next, let's calculate the calories provided by each macronutrient: Protein: 12g × 4 kcal/g = 48 kcal Fat: 14g × 9 kcal/g = 126 kcal Carbohydrate: 74g × 4 kcal/g = 296 kcal Total calories in 100g of the snack food: 48 kcal + 126 kcal + 296 kcal = 470 kcal Now, let's find the percentage of calorie content from fat: Percentage of calorie content from fat = (Calories from fat / Total calories) × 100 = (126 kcal / 470 kcal) × 100 ≈ 26.81% So, about 26.81% of the calorie content of this snack food comes from fat.

(c) Finding the grams of protein needed for the same fuel value as 25g of fat

We are given that 25g of fat needs to be replaced with protein to provide the same fuel value. First, let's find the energy content of 25g of fat: Energy content of 25g of fat = 25g × 9 kcal/g = 225 kcal Now let's find the mass of protein needed to provide the same fuel value: Energy content of protein = 4 kcal/g Mass of protein needed = Energy content of replacement / Energy content of protein = 225 kcal / 4 kcal/g ≈ 56.25g Therefore, about 56.25g of protein is needed to provide the same fuel value as 25g of fat.

Key concepts

Energy Content of Carbohydrates

When it comes to understanding how our body generates energy from food, it's essential to start with the basics: carbohydrates. Often the primary source of energy for many people, carbohydrates contain 4 kilocalories (kcal) of energy per gram. This unit of measurement, kcal, is commonly referred to as a calorie.

Simple carbohydrates, such as sugars found in fruits and sweets, and complex carbohydrates like those in grains and legumes, both provide the same amount of energy per gram. However, complex carbohydrates have the added benefit of providing fiber, which aids in digestion.

Energy Content of Fats

Fats, on the other hand, are calorically denser, harboring about 9 kcal per gram. This substantial energy content is why fats are so rich in calories and why they are considered an efficient form of stored energy in the body.

Due to their dense caloric content, fats are often targeted for reduction by those seeking to manage their weight. However, it's important to recognize that some fats are essential for health, aiding in the absorption of fat-soluble vitamins, and providing the necessary fatty acids that our bodies cannot produce on their own.

Caloric Contribution by Macronutrients

Understanding the caloric contribution of macronutrients is paramount for those managing their dietary intake. Every gram of protein provides 4 kcal, making its energy content equivalent to carbohydrates. This uniformity allows for easier comparisons when calculating dietary needs or restrictions.

Using the food label from a package, one can discern the caloric distribution among macronutrients and make informed decisions based on their energy goals, whether for weight management, athletic performance, or health conditions that dictate specific macronutrient requirements.

Macronutrient Comparison

Comparing macronutrients is insightful for anyone curious about dietary planning or understanding the energy yield of foods. Given equal masses, fats provide more than twice the calories of proteins or carbohydrates. This high-energy yield might explain why fat-rich foods are more satiating, leaving one feeling full for longer periods.

This comparison is crucial when optimizing diets for different objectives, such as increasing muscle mass, where more protein might be prioritized, or providing long-lasting energy, potentially making a slightly higher fat intake favorable.