If you've ever tried to lose weight, you’ve likely heard the common mantra: "Eat less, move more." While this advice may work for some people in the short term, it's not a one-size-fits-all solution. The reality is that weight management is complicated, and many factors—biological, psychological, and environmental—play a role in why we gain weight and struggle to maintain a healthy body size.
In this post, we’ll dive deeper into some of the key biological factors that contribute to weight gain and explore how multiple factors, like stress, mental health and, food relationship and choices also influence our ability to maintain a healthy weight.
The Biological Drivers of Weight Gain: It’s Not Just About Calories
When we talk about weight gain, most people immediately think of the simple equation: calories in versus calories out. While this model does have some validity, it overlooks the complexity of how our bodies actually respond to the foods we consume. It’s important to understand that weight gain is influenced by many factors—hormonal imbalances, genetics, gut health, and the quality of the food we eat. These factors, individually and collectively, affect how we metabolize and store energy.
1. Genetics and Learned Habits: How Both Shape Your Weight.
Genetics play a significant role in determining how our bodies store fat, how efficiently we burn calories, and how our metabolism functions. Studies have shown that heritability estimates of body fat range from 40% to 70% . This means that if you have a family history of obesity, you may be genetically predisposed to gain weight more easily.
Some genes influence hunger, while others affect fat storage. For example, the FTO gene, known as the "fat mass and obesity-associated gene," has been shown to increase the likelihood of obesity. People with certain variations of the FTO gene may have a higher appetite, a preference for high-calorie foods, and an increased ability to store fat.
And while genetics certainly play a role in our weight, it’s important to also consider the behaviors we develop during childhood. From a young age, we’re influenced by what we see and experience, whether it’s the size of the portions we’re given, the food choices we grow up with, or whether we become accustomed to an active or sedentary lifestyle. If you’re anything like me, you might find that some of those early habits are still with you today. For instance, I’ve always had the urge to snack while watching TV—a habit that’s so deeply ingrained that I have often not realized I’m doing it. To overcome this, I’ve learned to be mindful and make small adjustments, like sipping on tea or munching on raw veggies instead of reaching for chips or candy. It’s a lot easier to tweak old behaviors than to see them as the enemy.
There was a time in my life when I wasn’t making those conscious changes. I indulged in my cravings without a second thought, and over time, those habits took a toll on my health. I ended up gaining weight, developed symptoms of hormonal imbalances, and eventually became prediabetic. This is a real-life example of how our habits can sneakily lead to hormonal changes that impact our metabolism, appetite, and ultimately, our ability to manage weight.
2. Hormonal Imbalances: The Role of Leptin, Insulin, and Cortisol.
Hormones are powerful regulators of our weight and metabolism. Here are some of the most influential ones:
- Leptin: This hormone is produced by fat cells and signals the brain to stop eating when we’ve had enough food. However, in people with obesity, leptin resistance can occur, meaning the brain doesn’t respond to leptin’s "full" signal. As a result, people may continue to eat even when they’re not hungry, leading to overeating and weight gain.
- Insulin: Insulin helps regulate blood sugar and fat storage. Chronic overeating, especially of white breads and sugary foods, can lead to insulin resistance. When the body no longer responds properly to insulin, glucose (sugar) stays in the bloodstream instead of being used as energy. This leads to fat storage, particularly around the abdomen, contributing to weight gain.
- Cortisol: Often referred to as the "stress hormone," cortisol is released during times of stress. Chronic stress and high cortisol levels have been linked to abdominal fat accumulation, as well as an increase in appetite, particularly for high-fat, high-sugar comfort foods. This can create a cycle where stress leads to weight gain, which, in turn, leads to more stress.
These hormonal imbalances can make weight management much more challenging. Even with a balanced diet and exercise routine, some individuals may struggle to lose weight if their hormones aren’t functioning properly.
3. Gut Health: The Key to Metabolism and Weight Regulation
The health of our gut is more important than many people realize when it comes to weight management. Our gut microbiome, the collection of trillions of bacteria and other microbes living in our intestines, plays a significant role in how we process food, absorb nutrients, and regulate fat storage.
Research has shown that imbalanced gut bacteria (dysbiosis) can contribute to weight gain by affecting how our bodies metabolize food. One study found that individuals with obesity tend to have fewer beneficial gut bacteria and more harmful bacteria that can disrupt metabolism, leading to increased fat storage.
Additionally, gut health influences inflammation, which is linked to weight gain. Poor gut health can trigger systemic inflammation, which in turn can interfere with hormone function, including those that regulate appetite and fat storage.
I learned this firsthand during my own health journey. During the isolation period of the pandemic, I dedicated time to healing my gut by incorporating more vegetables and fermented foods into my diet, alongside supplements like collagen, slippery elm, marshmallow root, and L-glutamine. As I worked on improving my gut health, I started to notice positive changes—not just in my overall well-being, but also in how my body responded to food and weight management.
For me, this experience just confirmed the research I had studied that when it comes to managing weight, there’s more to the equation than just counting calories. The way our bodies process different foods, and how those foods interact with our gut and metabolism, can significantly influence our weight. In fact, not all calories are created equal.
The Quality of Calories Matters: Why 1,000 Calories of Broccoli Isn’t the Same as 1,000 Calories of Processed Snacks
When we talk about calories, it’s important to remember that not all calories are created equal. While traditional calorie counting has been a common method for managing weight, the type of food we consume plays a huge role in how our body processes, stores, and utilizes those calories. For example, your body will respond very differently to 1,000 calories of broccoli compared to 1,000 calories of ultra-processed snacks like cookies, chips, or soda.
To put it into perspective, you would have to eat over 28 cups of broccoli to reach 1,000 calories, compared to just half a bag of party-sized (13 oz) potato chips. Not only does the sheer volume of broccoli make it a more nutrient-dense choice, but your body processes it in a way that promotes better metabolic function.
The Impact of Whole Foods on Metabolism
Whole foods, such as fruits, vegetables, animal proteins, and whole grains, come with a nutrient-dense profile that supports your body’s natural processes. These foods contain fiber, vitamins, minerals, and antioxidants that help regulate blood sugar, reduce inflammation, and improve digestive health. When you consume a calorie-dense food like broccoli, your body is not only processing those calories for energy, but it’s also benefiting from the micronutrients that promote overall health and metabolic balance.
For example, fiber-rich foods like vegetables slow the rate of digestion, allowing your body to absorb nutrients more efficiently and regulate insulin levels. This leads to more stable blood sugar levels and prevents spikes in insulin, a hormone that, when elevated too frequently, can lead to fat storage (and cardiovascular disease, but that’s for another blog).
The Impact of Ultra-Processed Foods on Metabolism
On the other hand, 1,000 calories of ultra-processed snacks are often high in refined sugars, unhealthy fats, and additives, but lacking in essential nutrients like fiber, vitamins, and minerals. These foods are quickly broken down and absorbed by your body, leading to rapid spikes in both blood sugar and insulin levels. This can result in fat storage and increased cravings as your body tries to stabilize the insulin response.
Additionally, consuming large amounts of ultra-processed foods has been shown to negatively affect gut health, increasing inflammation and contributing to gut dysbiosis. Studies have shown that diets high in processed foods can lead to the overgrowth of harmful bacteria in the gut, further disrupting your metabolism and making it harder to maintain a healthy weight.
As you can see, the way your body processes calories depends not only on the quantity, but also on the quality of the foods you eat. I like to think of our body as a computer, and the food we consume as the code that tells it how to function. Whole, natural foods work in harmony with our cells and microbiome, helping everything run smoothly. In contrast, ultra-processed, manmade foods are like feeding a computer with broken, incoherent code—one that disrupts, inflames, and confuses the system, preventing it from functioning correctly or cohesively.
Energy Efficiency: How Your Body Handles Calories Differently
Another detail that many of us overlook is how much energy it takes just to process and break down the food that we eat. When you eat whole, nutrient-dense foods, your body expends more energy during digestion, a phenomenon known as the thermic effect of food (TEF). The thermic effect is particularly higher for protein-rich foods, which can require significantly more energy to metabolize compared to carbohydrates and fats. Likewise, nutrient dense vegetables like broccoli require energy for digestion so, although their thermic effect is generally lower than that of protein-rich foods, your body still has to work hard at breaking those compounds down during the digestion process.
On the other hand, ultra-processed foods require far less energy to process, meaning that a higher proportion of the calories are stored as fat rather than used for energy. On the other hand, ultra-processed foods require far less energy to process, meaning that a higher proportion of the calories are stored as fat rather than used for energy.
Psychological Factors: The Emotional Side of Weight Gain
While biology is a huge factor, psychological elements also significantly contribute to why we struggle with weight management. The relationship between stress, food, and mental health can create a vicious cycle that makes it even harder to maintain a healthy weight.
1. Food Addiction and Cravings
For some, food becomes a way to cope with emotions, a behavior commonly known as emotional eating. Certain foods, particularly those high in sugar, fat, or salt, can activate the brain’s reward system, providing temporary relief from stress or anxiety. Over time, this can lead to food addiction, where the desire to eat is driven by emotions rather than physical hunger.
Research shows that sugar-rich foods, in particular, stimulate pleasure centers in the brain, reinforcing overeating and contributing to weight gain. This becomes even more problematic when emotional eating turns into a habitual response to stress or depression.
I can relate to this during the cold winter months when the lack of sunlight and more isolated social life often leave me feeling down. While others may focus on preparing for warmer weather and their “summer bodies,” I find myself battling the “winter blues,” depression, and cravings. Depression and mental health are often overlooked in discussions about weight management, but they play a crucial role in our health and can make weight management even more challenging.
2. Depression and Mental Health
Mental health struggles like depression, anxiety, and stress can directly affect weight management. Depression can sap energy and motivation, making it difficult to exercise or prepare healthy meals. It can also lead to overeating as a means of coping with negative emotions, which often results in weight gain and can perpetuate depression.
3. Perfectionism and Societal Pressure
Society’s, often unrealistic, standards of beauty—especially the emphasis on slimness as a measure of worth—often lead to disordered eating patterns and a poor relationship with food. Many people, especially those in larger bodies may feel that they face fatphobia and weight stigma, which can lead to anxiety and low self-esteem. This societal pressure to look a certain way can cause individuals to engage in extreme dieting behaviors, setting them up for failure and contributing to yo-yo dieting.
The pressure to conform to an idealized body image can exacerbate mental health issues and disrupt a healthy relationship with food. This cycle of dieting, weight gain, and self-blame is both harmful and counterproductive when it comes to long-term weight management.
During times of my life when I was considered obese, everything felt harder than it needed to be. Not just physically, although I felt that too, but mostly just mentally. The self-criticism that I carried from the shame I felt as a fat woman, was like a dark shadow of a rain cloud that followed me everywhere I went. Brain fog and fatigue clouded every decision and muffled any desire to grasp the motivation I needed to regain control. This led to decades of desperate yo-yo dieting and rebound weight gain.
Eventually I learned that the biological and psychological factors driving weight gain are complex and multifaceted and that weight management is not just about eating less and exercising more. Food choices as well as hormonal imbalances, genetics, gut health, mental health, and societal culture all contribute to how we gain, lose, and maintain weight.
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