Decoding Your Plate: Why Are There More Calories When Cooked?

October 10, 2025 •

4 min read

According to a 2011 study published in the Proceedings of the National Academy of Sciences, researchers found that cooked food delivered more net energy than its raw equivalent when fed to mice, challenging traditional assumptions about calorie counts. This compelling finding sheds light on the often-misunderstood question of why are there more calories when cooked, and how cooking fundamentally alters the way our bodies process food.

Quick Summary

Cooking makes calories more bioavailable to the body, increasing the net energy gained from food. By breaking down complex structures, heat reduces the energy cost of digestion and boosts nutrient absorption. This explains why cooked meals provide more energy than raw ones, influencing diet and nutrition.

Key Points

Increased Bioavailability: Cooking breaks down complex food structures, making nutrients like carbohydrates, proteins, and fats more readily absorbed by the body.
Reduced Digestive Effort: The body expends less energy chewing and digesting cooked food, resulting in a higher net caloric gain from the meal.
Macronutrient Alterations: Heat gelatinizes starches in vegetables and grains and denatures proteins in meats and eggs, structurally changing them for easier enzymatic breakdown.
Enhanced Nutrient Absorption: Cooking can increase the absorption of certain nutrients, such as the beta-carotene in carrots and lycopene in tomatoes, by softening plant cell walls.
Dietary Energy & Evolution: Our smaller human digestive system is adapted for a cooked diet, which provided a more efficient source of energy to fuel larger brains throughout our evolution.
Added Ingredients vs. Cooking Process: The increase in available energy from cooking is separate from the calorie boost that comes from adding ingredients like oil or butter, which increases the total calorie count.
Method Matters: Different cooking methods have varying effects on nutrient retention and energy absorption, with methods like steaming or baking generally preserving more nutrients than boiling or frying.

Beyond the Calorie Label: The Science of Bioavailable Energy

The question of whether cooked food contains more calories than raw food is complex. While a standard calorie measurement (bomb calorimetry) shows a food's total potential energy, it doesn't account for the energy the body uses to digest and absorb those calories. The key distinction lies in bioavailable energy—the net energy the body can actually extract and use. Cooking increases this bioavailable energy by essentially 'pre-digesting' food for us, making it easier and less energy-intensive to process.

The Mechanisms of Increased Caloric Availability

Cooking is a transformative process that alters the chemical structure of food, making macronutrients more accessible to our digestive system. Here’s a closer look at what happens when you apply heat to food:

Gelatinization of Starches: Raw starchy foods like potatoes, grains, and legumes contain starches tightly packed within cell walls. These structures are resistant to our digestive enzymes. Cooking applies heat and moisture, causing the cell walls to break down and the starch molecules to swell and gelatinize. This process makes the starch easily accessible for rapid breakdown into simple sugars, significantly increasing the amount of energy we can absorb.
Denaturation of Proteins: Heat causes the complex, folded structures of proteins in meat, eggs, and plants to unravel, a process called denaturation. This makes the protein molecules much more vulnerable to our body’s digestive enzymes, which can then break them down into absorbable amino acids more efficiently. For example, cooking meat gelatinizes the collagen, making it easier to chew and digest.
Lipid Release: In foods like nuts and seeds, lipids (fats) are enclosed within tough cell walls. Cooking, such as roasting, can rupture these cellular structures, releasing the fats and making them more accessible for absorption. This can increase the net energy gain, as fats are a dense source of calories.

The Impact on Your Body's Energy Budget

The increased bioavailability of calories from cooked food is crucial from an evolutionary perspective. It's one of the reasons humans developed smaller digestive tracts compared to our primate relatives. Here’s how cooking affects the energy equation:

Lesser Digestive Effort: When food is cooked, our body doesn't need to expend as much energy on mechanical breakdown (chewing) and chemical digestion. This reduced 'thermic effect of food' means more net energy is left over for other bodily functions.
Influence on the Gut Microbiome: While raw food requires more work from our digestive system, some of the undigested starches and fibers end up feeding the bacteria in our gut. Cooking breaks these down earlier, allowing the human body to absorb the energy before the gut microbes can feast on it. This shifts who gets the calories—us or our internal bacterial population.

Raw vs. Cooked: A Comparison of Net Calories

To illustrate the difference in net energy, consider these examples. The actual increase in calorie count varies by food and cooking method, but the principle of increased bioavailability remains consistent.


Food Item	Raw State	Cooked State	Impact of Cooking on Digestibility
Sweet Potato	Contains resistant starch and tough fibers; requires significant chewing and digestive effort.	Heat gelatinizes starches, making them easily digestible. Net calorie absorption is higher.	High. Cooking drastically improves the breakdown of carbohydrates.
Meat (e.g., Beef)	Tough muscle fibers and collagen require high chewing effort and energy expenditure for digestion.	Heat denatures proteins and gelatinizes collagen, making it much softer and easier for enzymes to break down.	High. More protein is absorbed with less digestive effort.
Nuts (e.g., Peanuts)	Fats are encased in tough cell walls that resist digestion; some fat passes through undigested.	Roasting ruptures cell walls, releasing fats and making them more bioavailable. Less fat is excreted.	Medium to High. Increases lipid absorption.
Carrots	Retains high fiber content; less accessible beta-carotene.	Cooking breaks down cell walls, making beta-carotene more accessible for absorption.	Medium. While some water-soluble vitamins may be lost, antioxidants like beta-carotene become more available.

The Fine Print: Not All Cooking Methods Are Equal

It is important to differentiate between increasing bioavailability and simply adding extra calories. Frying food or cooking with large amounts of oil, butter, or sugar will certainly increase the total absolute calorie count. However, even without adding extra ingredients, the process of applying heat still makes the food’s inherent calories more available to the body. Methods like steaming and baking increase bioavailability without the significant calorie addition that comes from frying. Understanding this distinction is crucial for anyone managing their nutrition diet.

The Evolutionary Advantage of Cooking

For early humans, the ability to cook was a major evolutionary leap. By increasing the energy available from food, cooking allowed our ancestors to fuel larger, more energy-demanding brains. It also reduced the time and energy spent chewing and digesting, freeing up resources for other activities. The evidence suggests that our anatomy, with smaller mouths and guts, is a direct adaptation to a cooked diet. Learn more about the evolutionary significance of cooking.

Conclusion: The Final Word on Cooked Calories

Ultimately, when considering why are there more calories when cooked, the answer is not that heat magically creates new calories. Instead, it’s about efficiency. Cooking acts as a key processing step that increases the net energy our bodies can absorb by making nutrients more bioavailable and reducing the energy cost of digestion. For modern nutrition, this means that the preparation method of your food, in addition to the ingredients themselves, plays a significant role in your overall energy intake and dietary management.

Frequently Asked Questions

Total calories, or gross energy, is the total amount of potential energy in food, typically measured by burning it. Bioavailable calories, or net energy, is the amount of energy your body can actually extract after expending energy on digestion.

For most foods, cooking does increase the net available calories because it makes digestion more efficient. While different cooking methods and foods vary, the general effect of making nutrients more accessible to the body holds true.

There is no single answer, as it depends on the food. Some nutrients, like vitamin C in broccoli, are reduced by cooking, while others, like lycopene in tomatoes, become more bioavailable. A balanced diet with both raw and cooked foods is often recommended.

Cooking causes the starches in plant cells to gelatinize, swelling and breaking down their tough cellular structures. This makes the starches far easier for the body's digestive enzymes to break down and absorb.

Yes, frying food in oil or butter significantly increases the total calorie count. This is a separate effect from the increased bioavailability caused by the heat itself, which happens with or without added fats.

No, cooking does not destroy all vitamins. Water-soluble vitamins (B and C) are more susceptible to loss, especially with boiling. Fat-soluble vitamins (A, D, E, and K) are generally more stable, and some nutrients like antioxidants can become more available after cooking.

Yes, many evolutionary biologists argue that cooking was a crucial adaptation. By making food more digestible and calorically dense, it allowed early humans to fuel larger brains while spending less energy on digestion.