Is losing weight as simple as calories in, calories out? Ultimately, it may be gut microbes that make calories count

Is the saying “calories in, calories out“true? The short answer is yes, but the full story is more nuanced.

From the moment food hits your tongue to the moment it leaves your body, digestive system And gut microbiome work to extract nutrients. Enzymes in your mouth, stomach, and small intestine break down food for absorption, while microbes in your large intestine digest the leftovers.

“Calories in, calories out” refers to the concept that weight change is determined by the balance between the calories you consume and the calories you burn. This includes not only the number of calories you eat through appetite and absorb through digestion, but also how well those ingested calories are burned through metabolism.

Recent research shows that an important factor influencing people’s mood varying appetite, digestion and metabolism are biologically active leftover components of food, known as bioactives. These bioactives play a key role in regulating the body’s metabolic control centers: your brain’s appetite center, the hypothalamus; your gut’s digestive bioreactor, the microbiome; and your cells’ metabolic powerhouses, the mitochondria.

I am a gastroenterologist who has spent the past 20 years studying the role of the gut microbiome in metabolic disease. I’ll share how bioactive compounds in the diet help explain why some people can eat more but gain less weight, and I’ll share some diet aids to improve metabolism.

Worrying about appetite and digestion

Research has shown that consuming whole foods that are still in their packaging, original fibers and polyphenols—the cell envelopes and colorful compounds in plants that provide many of their health benefits—lead to more calories lost through fecescompared to processed foods that are “predigested”“converted by factories into simple carbohydrates, refined fats and additives.

This is one way that non-calorie factors affect the “calories in, calories out” equation, which can be beneficial in a society where calorie intake often exceeds need. By eating more whole foods and less processed foods, you simply eat more because more of those whole calories are going in. on the other side unused.

Fiber and polyphenols also help regulate your appetite and calorie intake through the brain. Your microbiome transforms these leftover bioactive compounds into metabolites—molecular byproducts of digestion—that naturally reduce your appetite. These metabolites regulate the same gut hormones that first inspired popular weight-loss drugs Wegovy, Ozempic, and Mounjaro, and control appetite through your satiety center of the brain, the hypothalamus.

Processed foods lack these bioactive substances and are further formulated with salt, sugar, fat And additives are deliciouswhich makes you long for it and eat more.

Mitochondrial maestros in the middle

A complete breakdown of calories also depends on how effectively your body burns them to power your movement, thoughts, immunity, and other functions – a process largely orchestrated by your mitochondria.

Healthy people usually have high capacity mitochondria that easily process calories to fuel cellular functions. People with metabolic disorders have mitochondria that don’t work so wellcontributing to increased appetite, less muscle And increased fat storage.

They also have less of a type of fat rich in mitochondria called brown fat. Instead of storing calories, this fat burns them to produce heat. Less brown fat may help explain why some people with obesity lower body temperature than those who are not obese, and why there is a decrease in average body temperature in the US since the Industrial Revolution.

Healthy mitochondria that burn more calories may also help explain why some people can eat more without arrivingBut this begs the question: why do some people have healthier mitochondria than others?

Your mitochondrial health is ultimately influenced by many factors, including those typically associated with general well-being: regular exercise, adequate sleep, stress management, and a healthy diet.

Who turned off the Metabo lights?

The latest nutritional research reveals the role previously underestimated dietary factors play in mitochondrial healthIn addition to the essential macronutrients (fat, protein and carbohydrates) and micronutrients such as vitamins and minerals, there are also other residual factors in food, including fibres, polyphenols, bioactive fats And fermentation productsare also essential for metabolism.

In contrast to a Western dietwhich often lack these bioactive compounds, traditional diets such as the Mediterranean area And Okinawan diets rich in foods nuts seeds fruits vegetables whole grains and fermented foods packed with these factors many bioactive compounds pass undigested through the small intestine to the large intestine where the microbiome converts them into activated metabolites. These metabolites are then absorbed, affecting the number of mitochondria in cells and how they function.

At the most fundamental level of cell biology, metabolites are turned on and off molecular switches in your genes through a process called epigenetics that can affect both you and your loved ones your descendants. When the metabolic “lights” come on, they activate the mitochondria which are responsible for a faster metabolism, effectively increasing the calories you burn.

Mind the microbiome gap

A healthy microbiome produces a full range of beneficial metabolites that support calorie burning brown fat, muscular endurance and metabolic health. But not everyone has a microbiome that can convert bioactive substances into their active metabolites.

Long term consumption of processed foodslow in bioactive substances and rich in salt and additivesmay compromise the microbiome’s ability to produce the metabolites needed for optimal mitochondrial health. Overuse of antibiotics, high stress And lack of exercise can also negatively impact the microbiome and mitochondrial health.

This creates a double nutritional gap: a lack of a healthy diet and a deficiency of the microbes to convert their bioactive compoundsAs a result, well-researched dietary approaches such as the Mediterranean diet may be less effective in some people with a disrupted microbiome, potentially leading to gastrointestinal symptoms such as diarrhea and a negative effect on metabolism.

In these cases, nutritional research examines the potential health benefits of different low carb diets that is allowed to circumvent the necessity for a healthy microbiome. Although the higher protein levels in these diets reduce the production of the microbiome of beneficial metabolites, the lower carbohydrates stimulate the production of ketones in the body. One ketone, beta-hydroxybutyrate, may function in a similar way to the microbiome metabolite butyrate in regulation of mitochondria.

Novel approaches that target the microbiome may also be useful for improving your metabolic health: butyric acid and other postbiotics to deliver preformed microbiome metabolites, personalized nutrition to tailor your diet to your microbiome, intermittent fasting to help restore your microbiome, and the future possibility of live bacterial therapies to restore the health of the microbiome.

Tools to convert fat into fuel

For most people, restoring the microbiome through traditional diets like the Mediterranean diet remains biologically feasible, but it is not always practical due to challenges such as time, cost, and taste preferences. Ultimately, maintaining metabolic health comes down to the deceptively simple pillars of a healthy lifestyle of exercise, sleep, stress management and a nutritious diet.

Nevertheless, some simple tips and tools can help make healthy diet choices easier. Mnemonics such as the 4 F’s of food—fiber, polyphenols, unsaturated fats, and ferments—can help you focus on foods that best support your microbiome and mitochondria with “leftovers.” Bioactive Calculators and Apps can also help you select foods to regulate your appetite, digestion and metabolism, thus rebalancing your calorie intake and expenditure.

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