Obesity rates have risen in recent decades.
In 2012, over 66% of the U.S. population had either overweight or obesity (
If you eat more calories than you need for energy, weight gain can result.
Here are 7 graphs that show that calories matter.
Source: Swinburn B, et al.
This study assessed changes in calorie intake and average body weight from 1970 to 2000. It found that in 2000 the average child weighed 9 pounds (4 kgs) more than in 1970, while the average adult weighed about 19 pounds (8.6 kgs) more (
The researchers found that the change in average weight equated almost exactly to the increase in calorie intake.
The study showed that children now consume an additional 350 calories per day, while adults consume an additional 500 calories per day.
Sources: Ogden CL, et al.
In the last 50 years, the average BMI has risen 3 points, from 25 to 28 (
Among U.S. adults, each 100-calorie increase in daily food intake is associated with a 0.62-point increase in average BMI (9).
As you can see in the graph, this rise in BMI correlates almost exactly to the rise in calorie intake.
Source: Ford ES, et al.
Some people believe carbs lead to weight gain, while others think that fat is the cause.
Data from the National Health and Nutrition Examination Survey suggests that the percentage of calories from macronutrients — carbs, protein, and fat — has stayed relatively constant over the years (
As a percentage of calories, carb intake has increased slightly, while fat intake has decreased. However, the total intake of all three macronutrients has gone up.
Source: Luscombe-Marsh ND, et al.
Research has shown a low carb diet can be effective for weight loss and provide numerous health benefits. However, the main reason it causes weight loss is calorie reduction.
One study compared a low fat diet to a high fat diet during 12 weeks of calorie restriction. All meal plans restricted calories by 30%.
As the graph shows, there was no significant difference between the two diets when calories were strictly controlled.
Furthermore, most other studies that have controlled calories have observed that weight loss is the same on both low carb and low fat diets.
That said, when people are allowed to eat until they feel full, they usually lose more fat on a very low carb diet, as the diet suppresses appetite.
Source: Sacks FM, et al.
This study tested four different calorie-restricted diets over 2 years and confirms some of the research above (
All four groups lost 7.9–8.6 pounds (3.6–3.9 kgs). The researchers also found no differences in waist circumference between groups.
Interestingly, the study found that there was no difference in weight loss when carbs ranged from 35–65% of total calorie intake.
This study demonstrates the benefits of a reduced-calorie diet on weight loss, regardless of the diet's macronutrient breakdown.
Source: Carels RA, et al.
To lose weight, many experts recommend eating 500 fewer calories than you need.
As you can see in the graph, there was a strong correlation between the number of days participants tracked calorie intake and the amount of weight they lost.
Compared with those who did not pay close attention to calories, those who tracked their calorie intake lost nearly 400% more weight.
This shows the benefits of monitoring your calorie intake. Awareness of your eating habits and calorie intake affects long-term weight loss.
Source: Levine J, et al.
This creates an energy gap, which is a term that refers to the difference between the number of calories you consume and burn.
There is also evidence that, overall, people with obesity may be less physically active than those who do not have obesity.
The researchers concluded that if those with obesity were to match the lean group's activity levels, they could burn an additional 350 calories per day.
The current evidence strongly supports the idea that a higher calorie intake can lead to weight gain.
While some foods may be more fattening than others, studies show that, on the whole, reducing calories causes weight loss, regardless of diet composition.
For example, whole foods may be high in calories, but they tend to be filling. Meanwhile, highly processed foods are easy to digest, and after eating a meal, you will soon feel hungry again. In this way, it becomes easy to consume more calories than you need.
While food quality is essential for optimal health, total calorie intake plays a key role in gaining and losing weight.