Is weight loss simply a math problem?
If you expend more calories than you take in, you will lose weight. This is a true statement.
After all, Kansas State professor Mark Haub, PhD, lost 27 pounds (12 kilos) in 10 weeks eating mostly twinkies and other processed "junk food" such as cookies, chips, and sugary cereal. He made sure he maintained a negative calorie balance and watched the pounds disappear. However, a subsequent article uncovered that he was funded by Coca Cola, calling into question the validity of his results.
But was it easy for him to stop eating each day when he reached his calorie target? How did he physically feel after eating such food? Would he have maintained his weight loss long term without significant hunger and cravings? And what about his long-term health?
These questions go far beyond calories in and calories out. But, at least in the short term, it appears that reducing calories - no matter what the type - can lead to weight loss.
Humans are complicated
When it comes to weight loss and food metabolism, the human body is complicated. We don't function like machines with simple inputs and outputs.
For starters, not all weight loss is the same. At Diet Doctor, we focus on healthy weight loss - meaning losing mostly excess fat mass, improving metabolic health, and doing it in an enjoyable and sustainable way.
Second, understanding how many calories we expend is complicated. The clearest example is the thermic effect of food. This has nothing to do with exercise or even metabolic rate. Instead, it is a measurement of how many calories you burn simply by digesting food.
Studies consistently show that protein has the highest thermic effect - meaning you burn more calories digesting protein than carbs or fat.
In addition, your resting energy expenditure can change based on what you eat or how you lose weight.
Weight loss in general, but especially loss of lean mass, can reduce your resting metabolic rate. When your metabolic rate is reduced too much, it can make it very difficult to maintain weight loss long term. But by losing mostly fat mass and maintaining or building lean mass, you can minimize the reduction in resting energy expenditure.
And what you eat can change your energy expenditure. Studies have shown that people eating ketogenic diets increase their total energy expenditure compared to those eating control diets. While controversy exists about how large of an effect this has, the data we have point to a probable metabolic advantage.
Plus - and this is important - what you eat can change how much you eat.
Kevin Hall, PhD, and colleagues performed a trial that allowed subjects to eat as much as they wanted, and carefully tracked their caloric intake. The study showed that participants ate 500 calories more each day when they ate ultra-processed foods, compared to less processed foods. The study authors attempted to match the percentage of calories from different macronutrients in both the ultra-processed and less-processed offerings, thus suggesting that the level of processing alone was the main cause of excess calorie intake.
Therefore, all calories are not the same when it comes to human nutrition and metabolism.
Hormones matter
Calories come from macronutrients, which can also affect your hormones in different ways.
Insulin is perhaps the most common example. Sugar and high-glycemic-index carbs tend to trigger a greater insulin response than protein- or fiber-containing carbs. And fat appears to have the least immediate insulin action, although it may have a mild longer-term effect, especially when eaten to excess.
Although still controversial, many studies point to hyperinsulinemia as being a cause of obesity. Whether or not it is proven as causal, elevated insulin levels are associated with obesity and metabolic dysfunction, and lifestyle therapies that reduce insulin levels can help with weight loss. Therefore, calories from foods that minimize insulin secretion may be better suited for weight loss in some individuals.
Further, studies report that elevated insulin levels can lead to a rapid decline in post-meal blood sugar, which then leads to increased hunger and calorie intake.
Foods can also affect our satiety ("fullness") hormones differently. Certain foods may trigger the release of leptin, CCK, PYY, GLP-1 and inhibit ghrelin (a "hunger" hormone) more than others.
These hormones don't appear to respond simply to the number of calories. Instead, protein-containing foods trigger satiety hormones more than other foods, and fibrous carbs trigger them more than refined carbs.
So, once again, we see that not all calories have the same effects.
Hunger matters
It's one thing to evaluate how your body processes and responds to calories. It's another thing to evaluate how your brain responds.
As we discussed in our podcast with Stephan Guyenet, PhD, your brain may be the most important organ for regulating weight loss and regain. Your brain can unconsciously alter feelings of hunger, hormone responses, and metabolic set points in reaction to different foods and degrees of weight loss.
And the foods you eat dramatically influence your hunger. As we detail in our guide on managing hunger while losing weight, your hunger will change depending on the number of calories and the macronutrient mix you eat, and your body's innate metabolic response.
Increased hunger due to forced calorie restriction may be the most common reason people fail to sustain weight loss.
Fortunately, you can follow certain principles that help reduce your hunger - and improve your satiety - while still getting all the nutrition you need and enjoying your meals. We call this our higher-satiety eating approach, and you can learn more in our introductory guide.
Higher-satiety eating prioritizes foods with higher protein percentages, lower energy density, higher fiber levels, and low hedonic factors. Eating this way allows you to decrease your calories with less effort. It's as if your body counts the calories for you.
Don't eat less; eat better
Instead of focusing on eating less, we suggest you focus on eating better. In the end, you may end up eating fewer calories, but you won't have to think about it. That means you don't have to track or weigh your food, which can reduce the feelings of restriction and hunger that come with it!
Some may argue that eating better in order to eat less is the same thing as counting calories to eat less. But we believe the mindset is different and your approach matters.
This is true for maintenance of weight loss, too. Beating back hunger by eating better is a sustainable way to avoid weight regain; a life of calorie counting to avoid regain is not only tedious, but it does not address hunger. It's a more difficult path that fails most people.
Once you understand how calories from various foods affect your metabolism differently, it should be clear why eating better can ultimately lead to healthy, sustained weight loss and improved metabolic health.
So, are all calories the same? Definitely not when you consider their effect on your health, your weight, and how they make you feel.
