If you’ve ever tried to lose weight, you’ve probably heard about the importance of “calories in versus calories out.”
This concept is based on the idea that as long as you eat fewer calories than you burn, you’re bound to lose weight.
What’s the ‘calories in, calories out’ model?
“Calories in” refers to the calories you get from the foods you eat, while “calories out” is the number of calories you burn.
There are three main bodily processes that burn calories:
- Basic metabolism. Your body uses most of the calories you get from food to sustain basic functions, such as your heartbeat. This is commonly referred to as your basal metabolic rate (BMR)
- Digestion. Around 10–15% of the calories you eat is used to power digestion. This is known as the thermic effect of food (TEF) and varies based on the foods you eat
- Physical activity. The leftover calories you get from your diet are meant to fuel your physical activity, including workouts and everyday tasks like walking, reading, and washing dishes.
When the number of calories you take in from food matches the number of calories you burn to sustain your metabolism, digestion, and physical activity, your weight will remain stable.
Thus, the “calories in versus calories out” model is strictly true. You need a calorie deficit to lose weight
Weight loss requires a calorie deficit
Once your body’s energy needs are met, extra calories are stored for future use — some in your muscles as glycogen, but most as fat. Thus, eating more calories than you burn will cause you to gain weight, whereas eating fewer than you need will cause weight loss
Health is more than just ‘calories in vs. calories out’
While the “calories in versus calories out” model matters for weight loss, not all calories are created equal when it comes to your health.
That’s because different foods have different effects on various processes in your body, regardless of calorie contents.
The source of calories impacts your hormones and health differently
Different foods can affect your hormone levels in different ways.
The differing effects of glucose and fructose serve as a good example. These two simple sugars provide the same number of calories per gram, but your body metabolizes them in completely different ways
A diet too rich in added fructose is linked to insulin resistance, increased blood sugar levels, and higher triglyceride and LDL (bad) cholesterol levels than a diet providing the same number of calories from glucose.
That said, fruit, which contains natural fructose along with fiber and water, does not have the same negative effects.
The types of food you eat affect how full you feel
Your nutrient intake impacts your hunger and feelings of fullness.
For instance, eating a 100-calorie serving of beans will reduce your hunger much more effectively than eating a 100-calorie serving of sweets.
That’s because foods rich in protein or fiber are more filling than foods containing lower amounts of these nutrients
This is why most processed foods that are rich in fructose but devoid of protein or fiber generally make it more difficult for you to maintain an energy balance.
The source of calories has different effects on your metabolism
Foods affect your metabolism differently. For instance, some require more work to digest, absorb, or metabolize than others. The measure used to quantify this work is called the thermic effect of food (TEF).
The higher the TEF, the more energy a food requires to be metabolized. Protein has the highest TEF, while fat has the lowest. This means that a high-protein diet requires more calories to be metabolized than a lower-protein diet does
Why nutrient density matters
The amount of nutrients a food contains per calorie can vary greatly.
Nutrient-dense foods provide higher amounts of vitamins, minerals, and beneficial compounds per gram compared with less nutrient-dense foods.
For instance, fruits are much more nutrient-dense than doughnuts. Calorie for calorie, fruit will provide a much larger dose of vitamins, minerals, and beneficial plant compounds.
Other examples of nutrient dense include vegetables, whole grains, legumes, meat, fish, poultry, dairy products, and unsalted nuts and seeds.
The “calories in versus calories out” model fails to take nutrient density into account, which is a good reason to doubt its relevance when it comes to your health.
The bottom line
From a strictly biological perspective, the “calories in versus calories out” model matters for weight loss.
You will only lose weight if you consume fewer calories than you burn, regardless of the types of food you eat.
However, this model fails to take nutrient density into account, which is highly relevant to your health. Moreover, different foods can impact your hormones, metabolism, hunger, and feelings of fullness differently, in turn influencing your calorie intake.Top of Form
What do we suggest? Focus on both! Eat a variety of foods you love and foods that are good for you within your calorie range. If you want to enjoy some chocolate during the day, then do so but ensure you are also getting in fruits, vegetables, proteins from plant sources or meat sources and whole grains.