Calories in vs calories out = weight loss. Sounds easy right?

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Obesity and being overweight is a major risk factor for all chronic diseases and losing weight, as well as changing body composition (i.e. increasing muscle mass) can have significant improvements in health, disease risk, overall wellbeing and quality of life. Fat tissue, especially around the mid section is pro-inflammatory and puts the most stress on vital organs, hence why it is a major risk factor and exacerbating factor for chronic diseases.

As the research literature accumulates around obesity and weight gain, it is without doubt that the mechanisms behind weight gain and obesity are extremely complex.

It involves a complex interaction between genes, diet, lifestyle and environmental factors. While the disease is not possible without excess caloric consumption, relative to the amount of calories burned, the factors that govern caloric intake and caloric output are complex and multi-faceted.

The “calories in vs calories out” equation is based on sex, age, physical activity and height. However, we know that the various factors which impact this equation are more complex than these four measurements.

We know that the “calories in vs calories out” equation always holds true because in research studies that put overweight individuals in metabolic wards, where researchers control participant’s caloric intake, participants always lose weight. The body will not defy basic laws of thermodynamics. You can’t lose weight without a caloric deficit and that is a fact.

However, humans don’t live in metabolic wards in hospitals. They are exposed to environmental factors that can have a large effect on their genes, caloric intake, energy expenditure and body composition. Humans exist within the many different context, which is why dietary changes for weight loss need to take this into consideration in order to make them as practical snd sustainable as possible.  

With this understanding, it allows us to have more realistic weight loss goals and allows people to realize that a lot of weight loss diets fail to address the multifaceted factors that affect our caloric intake and caloric output. These factors need to be addressed to ensure sustainable and maintainable weight loss. This is rather than taking an overly simplistic approach of “eat less and move more.” 

This blog post will outline the various diet, lifestyle and environmental factors that influence our caloric intake and energy expenditure, which in turn can contribute to weight gain and obesity. Once we understand these factors, we can modify our diet and lifestyle habits to increase weight loss, sustain weight loss, change body composition and prevent weight gain.

The factors affecting our caloric input are as follows:

Genes: There are various genetic mutations of certain genes (e.g. FTO-leptin, AMY1), that are associated with weight gain due to their role in regulating the functions of hormones and enzymes that are responsible for satiety, hunger, efficacy of the digestion/storage of carbs, sweet receptors in the mouth and blood sugar regulation. Some people carry these genetic mutations, which are inherited from their parents. 

The genetic expression of these mutations in an individual are significantly increased when combined with other risk factors for weight gain such as increased processed food intake, smoking, excess alcohol consumption, chronic lack of sleep, chronic lack of quality sleep, lack of exercise, increased sedentary behaviours and increased stress levels (i.e. obesogenic lifestyle). 

Also, while a person’s body fat set point (i.e. a complex set of hormonal and neuronal signalling within the body that regulates body fat), may have genetic origins, it is also dependent on a person’s environment. For example, a person who has overweight parents may have an increased likelihood of becoming overweight, but only if they are placed in an environment with the above risk factors for weight gain. This is likely the case as most overweight parents tend to have unhealthy habits that they model to their kids. 

Furthermore, a mother’s diet during pregnancy is a significant determinant of obesity risk in the foetus. During pregnancy, if a mother’s diet is inadequate, meaning she does not get the correct nutrients needed for proper foetal development, this sends signals to the foetus that in the outside world, food is scarce.

Therefore, epigenetic changes occur in the foetus that predisposes the child to extract more calories from food and have a higher propensity for fat storage. This is referred to as foetal programming. From an evolutionary perspective this is an extremely useful adaptation. However, in our modern world, with a 7-eleven at every corner, this is a recipe for disaster. Once a child becomes obese, it is very unlikely that they will lose the weight going into adulthood.

The above genes and genetic predispositions may explain why parents who are overweight tend to have children that are also overweight. However, just because you have a genetic predisposition to something, doesn’t mean these genes will actually manifest to cause weight gain. As mentioned above, the expression of genes are highly dependent on environmental factors. It is said that genes load the gun and environmental exposures pull the trigger. Depending on our environmental exposures, can determine whether certain genes are expressed or not. This is called epigenetics. This means that genes coding for obesity may only be expressed or “turned on” in the backdrop of an obesogenic lifestyle. Conversely, these genes may not be expressed in the context of a healthy diet and lifestyle. 

Epigenetics is somewhat comforting because it means that disease causing genes are not set in stone and our diet and lifestyle has a huge impact on how our genes manifest.

Lastly, research is also starting to show that the bacteria that inhabit our guts can turn on and off these obesity genes, govern how much calories we extract from certain foods, effect food cravings, as well as regulate metabolic rate and our satiety hormones (e.g. leptin, insulin, ghrelin). The composition of bacteria in our gut plays an important role in our gut health and our overall health. In fact, disruptions to the healthy balance of bacteria in our guts are being linked to more and more chronic health issues and diseases.

Our diet and lifestyle can significantly impact our gut flora composition, and a disrupted gut flora due to poor habits could be a determining factor behind weight gain due to their interaction with our genes, calorie absorption, metabolism and satiety hormones.

We initially inherit our gut bacteria from our mothers as we pass through the birth canal. Breast-feeding is also another way in which our mothers pass on their gut bacteria to their children. This may be one reason why we see a correlation between obesity and formula fed and C-section babies.

This is also another reason as to why mothers who are obese, are likely to have children that are also obese, as they may pass on certain obesogenic strains of bacteria that can predispose a child to obesity when exposed to modern lifestyle factors.

Food palatability: The human brain is hard-wired to be motivated by certain key goals that supported the survival and reproduction of our ancestors. One of these key goals is of course food intake.

When our brains accomplish a key goal that is hard wired in us because it is essential to our survival (e.g. food intake), a powerful brain chemical called dopamine is released. Dopamine is a “reward” chemical in the brain and after its release, it causes you to become more likely to execute specific behaviours that are essential to your survival, the next time you find yourself in a situation with sensory cues associated with carrying out that specific survival behaviour. These cues include sounds, smell, taste and location. This is a reason as to why you may crave certain foods just at the smell of them or if you are in a location where you usually consume a particular type of food.

Dopamine causes you to become more likely to execute specific behaviours that cause its release, when environmental cues are provided. In this case, it could be the sight and smell of certain foods.

The larger the surge of dopamine, the more motivated you will be the next time you encounter those cues. This is well illustrated by highly addictive drugs like crack cocaine and methamphetamine, which cause an immense release of dopamine that motivates drug-seeking behaviours. Addiction, at its core, is a very strong craving.

When we consume food, sensors in the mouth and small intestine detect the glucose, fructose, fatty acids, and amino acids in starch, sugar, fat, and protein and send a signal to the brain that releases dopamine. And the more concentrated those nutrients are in a food source, the greater the surge in dopamine.

From an evolutionary perspective, the release of dopamine in response to high calorie, highly palatable, sweet and fatty foods, makes sense. When we were hunter gatherers, food was scarce and when we came across calorie dense foods like sugary fruits and honey, the dopamine surge was crucial to our survival as it made us splurge on these foods because we didn’t know where our next meal was going to come from. It also caused an override of our normal satiety signals in the brain so we could stock up on calories. Now in the modern world, where high calorie and palatable food is so accessible, this evolutionary response leads to weight gain.

Highly processed, high calorie foods such as foods like chips, fries, bacon, cookies, cake, ice cream, and chocolate, deliver exactly what our brains are instinctively looking for, concentrated starch, sugar, fat, salt, and protein, which is why we crave these foods when we see them, hear them, smell them and find ourselves in locations/situations where we are used to consuming them. This is not a coincidence that these foods are manufactured in this way. Food companies’ hire scientists to manufacture foods that stimulate reward centres in our brains.

Interestingly, chocolate is the most frequently craved food among women, and it’s also a common craving for men. From the brain’s perspective, this isn’t hard to understand. Chocolate is not only a highly concentrated source of fat and sugar; it also contains a chemical called theobromine. Like its cousin caffeine, theobromine is a mild stimulant that acts on the same brain pathway as dopamine.

As you can see, ultimately, our brain and its reward pathways are a huge driving factor of weight gain. Everyone talks about insulin, leptin and other hormones, however the malfunctioning of these hormones is usually a downstream effect of consuming too many processed foods, which is driven by our brain’s reward systems.

Mental and emotional wellbeing: Stress and uncomfortable emotions can lead to stress/comfort eating, which usually takes the form of processed food that is high in calories. As shown above, these foods increase the release of reward chemicals in the brain such as dopamine, which can give a person temporary comfort and numbing from underlying emotional issues. This is why mental health issues are associated with weight gain and decreased weight loss. Weight gain then exacerbates the issues further. 

Hormonal balance: Fluctuations in hormones can have a large effect on caloric intake due to increases in appetite. The most common example is in women who experience PMS can get sugar, fat and salt cravings before their period. This can increase caloric input once a month, which overtime can lead to weight gain. PMS usually results from a low amount of progesterone production during a female’s cycle due to impaired ovulation and an overproduction of estrogen. This is usually driven by poor diet and lifestyle habits.

Poor sleeping habits: This factor is strongly associated with weight gain, obesity and impaired weight loss. It is one of the most important factors aside from diet. This is because chronic lack of sleep and good quality sleep leads to fatigue. This impairs people’s motivation to eat healthy, it increases cravings for sugary food because the brain wants an energy hit and it also increases the likelihood of a person making poor decisions around their health. 

Going to bed later increases the amount of time available where a person could snack, and it also disrupts the normal functioning of our satiety hormones like leptin, which means we may take longer to feel full at a meal leading to overeating. Moreover, snacking done late at night is rarely in the form of healthy food that is low in calories. It is also usually in front of a screen, which then starts to act as a food cue. 

Lastly, the fatigue resulting from a lack of sleep affects our exercise habits and decreases our ability to handle our stressors, leading to stress/emotional eating.

Time poor, busyness and stress: This causes people to be less conscious of food choices and eat on the run. This results in people underestimating their caloric intake because they are not being conscious around their food choices. This often leads to people putting on weight without understanding why, as well as decreased weight loss. 

Also, being time poor and busy causes a lot of people to make choices around their diet based on taste, convenience and cost. When this happens, the food choices are likely calorie dense and nutrient void because processed food is cheap, convenient and tastes good. It also leads to an overall decrease in home cooked meals, which is associated with weight gain due to an inability to control ingredients and portion sizes from takeout/restaurant food. 

Furthermore, stress can often lead to stress eating, where the person aims to seek comfort in calorie dense food that gives them a dopamine surge. To make matters worse, when we are stressed, we burn through our glucose stores, therefore we crave sugary foods to replenish what we lost and get an energy hit. 

Lastly, stress can also impair leptin and insulin sensitivity, leading to a loss of satiety when eating food, as well as a decrease in metabolic rate.

Lack of priority around healthy habits: People often prioritise many other things in their lives over their health and wellbeing, which often becomes neglected, yet it is the most important thing in their lives. This can lead to weight gain and impaired weight loss.

Good health allows us to live our best life and be the best version of ourselves. Prioritising health and wellbeing comes down to a person’s value system. Changing a person’s value system, which puts health and wellbeing at the top of their value hierarchy, is absolutely essential to changing diet and lifestyle habits for the better.

Our values affect our thoughts, emotions and behaviours, hence changing our values can have a profound effect on our diet and lifestyle. Changing values are easier said than done though. Especially in a society that tells us to create values around things like money, busyness, status, material goods and career success. Chasing these things often comes at the expense of good health and a healthy weight. 

Lastly, to many people, good habits to promote wellbeing/weight loss are often perceived by people as high effort for little reward, meaning they require effort but don’t give people any real instant gratification or any of the things we are told to value in society. This decreases motivation to perform these behaviours. Especially in a world driven by the pursuit of pleasure and instant gratification.

However, people don’t realise that looking after their health on a daily basis actually allows them to be the best versions of themselves because being sick and run down means a person can’t live their best life. 

Food quality: To maintain a healthy weight or even lose weight, it is essential to eat nutrient dense, healthy, good quality whole-foods, which increases satiety levels, while taking in minimal calories. Whole foods from animal and plant-based foods contain good sources of protein and fibre, which take time to digest and take up a lot of space in the gut. This activates stretch receptors, which tells the body it has enough food and it can dampen hunger signals and increase satiety signals.

Furthermore, when we eat whole foods, especially foods like fruit and vegetables, not all calories are absorbed because of the presence of fibre, which inhibits absorption. Also, whole foods tend to be more “complex” in their structures, which in turn make it harder for the body to digest and absorb fully.

This is compared to eating processed foods that are high in calories, low in nutrients and therefore not very satiating. These types of foods can easily lead to overeating and therefore overshooting caloric intake. When we eat processed foods, most of the calories are absorbed. This is because the very nature of processed foods means that the body can break it down and absorb it easily, without them taking up space in the gut.. This is a reason why processed foods, especially sugary drinks are not very satiating. Processed foods are absorbed quickly, take up less space in the gut and contain a lot of calories per gram ingested.

Lastly, because whole-foods are so filling, when we eat a diet high in whole-foods, we quickly feel full without consuming too many calories. This is why during weight loss phases, eating lots of foods like protein and vegetables that make us feel full are so important. It allows us to interact with our food in a natural way (i.e. eat until we are full without having to worry about caloric intake – which is how we would eat when we were hunter gatherers when food was not readily available). This is opposed to counting calories and using voluntary calorie restriction when we try to lose weight. From an evolutionary perspective, voluntary caloric restriction to lose weight is not natural and not in line with our genetic makeup, however in our modern world, we have had to do this due to excessive food availability and our strong drive to eat these foods because our brains are genetically hardwired to crave them for survival. Therefore, as mentioned, we need to try to eat food that allows us to eat until feeling full, with as little calories as possible, so that we don’t have to actively restrict food and calorie intake.

Food labels: When people begin to calculate the “calories in” part of the “calories in vs out” equation for weight loss, they normally base it on food labels and google. However, this can often be extremely inaccurate, which can lead to feelings of disappointment when a person is not reaching their weight loss goals.

Firstly, this is because the number of calories shown on google or food label for a given food, are determined by devices that have been shown to be at least 20-25% off the actual caloric amount of that given food. Secondly, whole foods are very variable (e.g. size), which can affect their calorie content. Thirdly, as seen above, just because you eat a food, doesn’t mean all the calories from that food are actually absorbed. There is a difference in calorie absorption of processed foods and whole-foods. All of these factors can lead to an unexpected overconsumption of calories leading to weight gain and impaired weight loss.  

Lastly, regardless of the type of food, there are many factors that can affect a person’s absorption of food in general, therefore having an effect on their caloric intake. These include factors such as stress, the composition of gut bacteria, age and even certain types of medications. In saying that, we also know that cooking, juicing and blending whole foods can make nutrients more available to the body, as well as increase the number of calories absorbed from a given food.

Socioeconomic class: People of lower socio-economic status have an increased risk of chronic disease and one of those diseases is obesity. This seems to be because healthy food is usually more expensive than processed food, as well as a lack of education around healthy eating and food preparation. Also, people of lower socio-economic classes tend to be more stressed and time poor, which leads to an increased likelihood of turning to calorie dense, fast food options. This can all lead to weight gain and decreased weight loss. 

Knowledge around cooking and eating a healthy diet: This is largely dependent on a person’s socioeconomic class and what was modelled to them as a child. As well as the information that has been exposed to them over their lifetime. A lack of knowledge can lead to increased intake of calorie dense and unhealthy foods, leading to weight gain, impaired weight loss and poor health outcomes. 

Medications: Pharmaceutical medications are ubiquitous in our modern world due to the chronic disease epidemic. Many medications have been shown to increase appetite and affect metabolic rate, which in turn can lead to weight gain and hinder weight loss. A prime example of this is the contraceptive pill.

The factors affecting our caloric output are as follows:

Decreased NEAT: NEAT stands for non-exercise activity thermogenesis and it is all of the activity we do on a daily basis that is not pre-planned formal exercise, however we do it as part of our daily lives (i.e. incidental movement). It is unstructured activity that results in energy expenditure. 

These days, many people work desk jobs that are very sedentary in nature, which therefore decreases NEAT and decreases overall energy output for the day. Leading to weight gain and decreased weight loss. When we were hunter gatherers, daily movement was essential to our survival (e.g. hunt, gather, protect ourselves). 

Also, people are not as active and “outdoorsy” as they once were. I think things like technology are keeping us indoors a lot. 

Lastly, as we age, due to low energy and poor mobility, we move around less. 

Note: High levels of NEAT per day burns more calories than formal exercise and being sedentary all day. 

Basal metabolic rate (BMR): BMR is the amount of energy per unit time that a person needs to keep the body functioning at rest. It makes up approximately 60% of our caloric output and it is related to our age, sex, weight, hormonal status (i.e. thyroid, sex hormones, leptin, cortisol), gut bacteria, muscle mass and whether we are stressed, injured or sick.

A “slow metabolism” is also usually blamed for weight gain and while it does differ from person to person, due to the factors above, for a given life stage, it doesn’t vary as much as people think, which is why studies show it is not a good predictor of weight gain. The other factors affecting caloric input discussed in this post are greater determinants of weight gain.

As a person puts on more weight, their BMR and metabolic rate increases because more energy is required to move and sustain a heavier body. As a person loses weight, their BMR will drop, which is why they will have to decrease their caloric intake as well. This is also a way of the body trying to conserve energy as weight loss is seen as a stressor on the body. The body prefers to put on weight because fat stores are a source of energy when food is not available. These mechanisms developed to help us survive in the wild when food was scarce. Now these mechanisms are sent into overdrive with increased food availability that are high in calories.

Based on this, taller people have faster metabolisms than smaller people. People with lots of muscle mass have higher metabolisms because muscle requires a lot of energy to sustain. This is why strength training is so good for weight loss as it raises metabolic rate and increases muscle mass. Also, as you do get older, your metabolism slows, therefore increasing the risk of weight gain. While you can’t control your ageing process, you can however control what you put in your mouth, which means as you age you may have to eat less than what you used to in order to maintain a healthy weight. 

Exercise: Many people lack a consistent and well-planned exercise regime, which is not only vital for increasing energy output and maintaining a healthy weight, it is also essential for good health. 

On top of this, as seen above, poor sleeping habits affect our exercise habits and caloric output leading to weight gain, as well as impaired weight loss. This is because when we don’t get enough sleep, we are fatigued and less likely to move during the day and engage in exercise. Stress can also affect adherence to an exercise regime.

Lastly, as we age, we exercise less, and the intensity/duration often drops, which is due to limiting factors like mobility. This affects weight gain and weight loss capabilities. 

Note: Caloric output from exercise depends on the type of exercise, duration, frequency and intensity. However, the significance of the caloric output for weight loss is not as much as people think, yet it is still very good for our health. 

Strength training appears to be the best form of exercise for weight loss. This is because increasing muscle mass increases a person’s resting metabolic rate as muscle require a lot of energy to house in the body and repair after a workout. Therefore, if a person is not over consuming calories, their fat stores will be used as energy to maintain their muscle mass (as long as adequate protein is ingested to support muscle repair and growth). 

Lastly, as a person loses more weight, their caloric output during exercise becomes less, because they are moving less weight, which requires less energy. This is why the duration, difficulty and intensity of exercise must increase as weight loss occurs.

Thermic effect of food (TEF): The thermic effect of food is the energy required for digestion, absorption, and disposal of ingested nutrients. Its magnitude depends on the composition of the food consumed. Whole foods take more energy to digest, absorb and dispose in the body due to nutrients like protein and fibre. Protein dense food (i.e. animal based products) require the most amount of energy to digest and they are very satiating, which is why protein is a very important part of weight loss diets and protecting against weight gain. Processed food, due to its very nature of being processed, requires a lot less energy to digest and absorb, therefore increasing the likelihood of weight gain and decreased ability to lose weight. 

It must also be noted that it is commonly thought that eating small meals throughout the day “boosts” metabolic rate due to the thermic effect of food. However, as long as the caloric intake between two people is the same, food frequency seems to have little effect on overall calories burned throughout the day.

Hormonal status: Hormonal changes throughout a person’s lifetime can affect their energy output and BMR, which can contribute to changes in weight. For example, people with hypothyroidism (mainly affecting females) have a slowing of their metabolic rate. Also, as females age, they hit menopause and experience a natural decline in estrogen and progesterone production, which slows metabolic rate. Another example is in males who have low testosterone levels. This slows metabolic rate, as well as increases muscle loss and decreases muscle growth.

The effects of hormones on metabolism is certainly a contributing factor to weight gain and impaired weight loss, however it is not as large as one may think and factors like NEAT and exercise affect caloric output to a far greater degree and are more controllable to change. Therefore, these need to be a focus during weight loss, as well as focusing on controllable factors around caloric intake. Lastly, diet and lifestyle habits often affect hormone status, therefore good habits will promote healthy hormonal balance. 

Note: If your hormones are affecting your caloric output, then you may need to reduce your caloric intake more so than someone else at the same weight without hormone imbalances. You can’t always completely control your hormones, but you can control what you put in your mouth. 

Wrapping up:

Your average weight loss diet and fad diets purely focus on calories, while neglecting the fact that although a person needs to restrict calories, they also need certain nutrients from wholefoods to fuel their body and support metabolic processes for good health. This is why fad diets can lead to nutrient deficiencies. 

They usually involve severe caloric restriction that if adhered to, will lead to weight loss, however they fail to address and change all of the factors and poor habits that have led to weight gain in the first place, such as all the things listed above.

The severe caloric restriction makes them unsustainable and the lack of education around changing bad habits to good habits, usually leads to rebound weight gain. Once a person finishes or fails on the diet and goes back to their “old diet and lifestyle,” they are likely to put the weight back on, plus a few more kilograms then what they started with. 

The body does this because this mechanism ensured human survival when food was scarce. The human body prefers to put on weight rather than lose it because fat stores are a source of energy when food is not available. These mechanisms developed to help us survive in the wild when food was scarce. Now these mechanisms are sent into overdrive with increased food availability that are high in calories. 

Therefore, when we decide to lose weight, especially if caloric restriction is severe, the body sees it as a stressors and thinks that food is scarce, which is why you feel hungry, irritable and tired, because the body tries to conserve energy and down regulate all “non-survival” mechanisms. The body will do all that it can to regain that lost body fat. This explains why it is so hard for people to lose weight and keep it off. Your body is literally working against you and doing all that it can to resist the loss of more body fat.

Once a person begins to give into their hunger and abandon their caloric deficit, the body will put back on the lost weight, plus a few more kilograms just in case food becomes scarce again (i.e. caloric restriction). The hunger cravings are obviously more intense with a greater caloric restriction and a greater amount of weight to lose. Slow and gradual weight loss leads to less hunger cravings as it allows the body to adjust its set point slowly, without it being perceived as a stressor. This process is also made easier by eating foods that are high in nutrients and very satiating, but are low in calories (i.e. protein and vegetables). A body that feels nourished and full is less likely to think ‘food is scarce.’ Eating these types of foods allow us to interact without food in a natural way, such as eating until we are full and not having to worry too much about caloric intake. This is opposed to voluntary caloric restriction.  

Many people often find themselves yoyo dieting over many years and this eventually causes the body to become more resistant to weight loss and it makes a person feel the effects of caloric restriction more heavily making weight loss harder (e.g. fatigue, hunger, cravings etc.). 

Yoyoing “breaks your metabolism,” which is a person who has been yo yoing all their life may have to restrict their calories more than someone else at the same body weight (who has never yoyo-ed) in order to lose weight. Or their caloric intake that once worked to lose weight when they were younger doesn’t anymore. Or once they lose weight, in order to maintain it, they may need to eat less calories than someone else at the same body weight who has never been overweight. 

Lastly, losing weight very quickly can actually damage a person’s metabolism, where their body takes up to 7 years to re-adjusts to a new set point. This means the adaptive mechanisms of the body in response to a lowered caloric intake (e.g. fatigue, cravings, hunger and lowered metabolic rate) persist, even when the person is at a new body weight. This makes sustained weight loss extremely difficult.

As a health practitioner, I specialise in helping people lose weight in a practical and sustainable way, without using meal replacements, as well as without removing and demonizing whole food groups, as these things are not sustainable. My aim is to help people address all of the underlying causes affecting their calories taken in and calories out. I want people to learn how to eat a varied whole-food, balanced diet, with lots of different foods, along with healthy serving sizes (as whole-foods still have calories) and good habits around their eating patterns. This increases the likelihood of them losing weight, changing body composition (i.e. increasing lean mass and losing fat) and most importantly, keeping it off. 

Call Oak Health today or book an appointment online to find out how evidence based, practical and sustainable diet and lifestyle interventions can help you lose weight, change your body composition and keep it that way. You may also want to enquire about the 8-week weight loss program.

For more information Oak Health’s approach to weight loss, check out the treatment page here.