Obesity is a major risk factor for all chronic diseases and losing weight can have significant improvements in health, disease risk and overall wellbeing. Loosing weight will always increase health markers and parameters. Australia is currently in an obesity epidemic, which is a large river behind the chronic disease epidemic. We need a major shift in our diet and lifestyle because weight gain is primarily due to diet and lifestyle choices.
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 and it is simply not a disease of laziness and poor self control.
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.
Furthermore, the energy balance equation tells us about body weight, but doesn’t tell us about body composition, which is governed by sex hormones, macros like protein, type of exercise done, age, medications used (absorption and messing with satiety/hunger hormones).
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 physics.
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.
By understanding the main factors that govern our caloric intake and caloric out, it allows us to have more realistic weight loss goals and allows people to realize that simply eating less and moving more, will not always lead to their desired results, as things are a little more complex.
This 3 part series will outline the various diet, lifestyle and environmental factors that influence our caloric intake and energy expenditure, which in turn, when combined together, can contribute to weight gain and obesity. It is with this understanding; we can better understand how to modify our diet and lifestyle habits to increase weight loss, sustain weight loss and prevent weight gain.
Factors effecting “calories in”
Increased caloric intake beyond an individuals caloric needs is one of the main determinants of weight gain and there are 9 main factors that lead to increased caloric intake. People who are overweight or obese will likely have most of these 9 factors present.
Our genetic make up can have a large impact on both our caloric intake and output. There are a few genes associated with obesity and weight gain, which are outlined below.
Humans contain a gene called the FTO gene (aka the fat gene). This gene helps to control body fat percentage through its role in regulating the actions of a hormone called leptin. Leptin is released from fat cells and it is our many satiety hormone, therefore it suppresses hunger and tells us to stop eating when we are full and have consumed enough energy.
Genetic mutations of this gene have been linked to obesity and type 2 diabetes. Mutations in the FTO genes lead to sloppy control over leptin and leptin resistance, which means the brain is less sensitive to the signals of leptin, causing increased appetite and therefore increased caloric intake when we eat.
Another genetic mutation associated with obesity and type 2 diabetes is the AMY1 gene. The AMY1 gene is responsible for producing enzymes that digest carbohydrates in our body. This means that we all have a certain genetically determined “tolerance” of carbohydrates. People with more copies of the AMY1 gene, tend to tolerate carbs better, meaning they use carbs for energy production more efficiently, rather than going to fat stores. They also tend to have a better insulin response to carbohydrates and carbohydrates taste sweeter in their mouth, therefore decreasing the chances of over-eating.
Many copies of these genes are found in populations that have high amounts of carbs in their native diets, such as the Japanese (i.e. rice). However, in a world where processed, high calorie carbs are readily accessible, a person with less copies of this gene can be at increased risk of weight gain if they consume too many processed carbs.
Lastly, a mothers diet during pregnancy is a significant determinant of obesity risk in the fetus. During pregnancy, if a mothers diet is inadequate, meaning she does not get the correct nutrients needed for proper fetal development, this sends signals to the fetus that in the outside world, food is scare.
Hence epigenetic changes occur in the fetus that predisposes the child to extract more calories from food and have a higher propensity for fat storage. This is referred to as fetal programming. From an evolutionary perspective this is an extremely useful adaptation and helped with our survival as a species. 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 loose 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.
It is said that genes load the gun and environmental exposures pull the trigger. This means that not all of our genes are set in stone and depending on our environmental exposures, can determine whether certain genes are expressed or not. This is called epigenetics.
It means that genes coding for obesity may only be expressed or “turned on” in a obesegenic lifestyle, such as high consumption of processed foods, lack of exercise, smoking, alcohol consumption, stress, lack of sleep etc. Based on this idea of epigenetics, parents who are overweight tend to have children who are overweight because they are likely to expose them to unhealthy diet and lifestyle habits, which has driven their own weight gain.
Conversely these genes may not be expressed or “turned on” in the context of a healthy diet and lifestyle. Therefore despite predispositions, weight gain may not manifest in the presence of protective diet and lifestyle habits. 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.
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). They may also influence food cravings.
The composition of bacteria in our gut play an important roles 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 could be a contributing factor behind weight gain due to their interaction with our genes, calorie absorption, metabolism and satiety hormones. For example, poor composition of gut flora may turn on obesity genes, impact metabolic rate via decreased thyroid hormone production, increase the amount of calories we extract from food, increase the production of chemicals that travel to the brain and increase food cravings for processed food, as well as decrease the functioning of satiety hormones like leptin in the brain. Conversely healthy gut flora may do the opposite.
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 “obesegenic strains” of bacteria that can predispose a child to obesity when exposed to modern lifestyle factors.
Other factors that can lead to poor gut health include overuse of anti-biotics (due to their disruption on the gut flora), a diet high in processed foods, chronic lack of sleep, excess alcohol consumption, lack of exersize, chronic stress, lack of fruit and vegetable intake, past history of acute gastroenteritis, micronutrient deficiencies resulting from a poor diet and overuse of certain pharmaceuticals such as ant-acids, corticosteroids, blood pressure medications, illicit narcotic drugs and opiate drugs.
Lastly, an unhealthy gut microflora balance, caused by the factors listed above, leads to decreased leptin sensitivity. Poor gut flora causes inflammation that travels to the brain and disrupts the receptors for leptin, which is our main satiety hormone. This leads to overeating because the brain doesn’t respond effectively to leptin secretion, which is released to tell us when we are full. For these reasons it is probably why obese people have a very different gut flora composition to lean people.
2) Body fat set point
Another factor worth mentioning is the concept of a body fat set point. A person’s set point is the set amount of body fat that their body prefers to store, defend and maintain. It is a complex set of hormonal and neuronal signalling within the body that regulates body fat and is likely to be somewhat genetically inherited. Which is yet another potential explanation as to why overweight parents have overweight kids. But once again, genes may only play part of the role, where as diet and lifestyle factors may be a bigger determinant of weight gain. Therefore children may only develop obesity in an obesegenic environment (e.g. lots of processed food, lack of exersize, lack of sleep, stress, which are more likely to happen if they have that modeled from their parents). A child may lower their set point if they are exposed to good diet and lifestyle habits (low calories, nutrient dense foods).
When you eat below the amount of calories needed to maintain your set point (i.e. in weight loss), the body thinks it is starving.
It begins to put into place metabolic processes to help regain the lost calories. It does this by slowing your metabolic rate (decreasing thyroid function), increasing fatigue/lethargy (so you don’t move around as much) and increasing intense hunger cravings/thoughts about food. Your body also naturally decreases “unnecessary” movements that burn calories such as fidgeting and sitting up straight (i.e. people will naturally slouch while sitting as more energy is required to sit up straight).
This is an evolutionary mechanism that ensured our survival as a species as we used to live in food scarce environments where food was not always available. These evolutionary mechanisms kept us alive, reduced energy expenditure and drove us toward seeking food. However, these days food is readily accessible, especially high calorie, palatable foods. Therefore when your body is craving food and especially calories (in order to regain the bodies set point), it is going to crave the highly processed and highly palatable, high calorie foods. When we used to live in food scarce environments, once we found food we would binge until we were full and these foods were not calorie dense. If we were lucky, the most calorie dense food we would find is fruit and honey. However now days, food is readily accessible that is high in calories and tastes good. This demonstrates how there is a large mismatch between our genes/genetic makeup and our modern environment.
This is why it is so hard for people to lose weight and voluntarily restrict their calories because once this happens, the body thinks it is starving and kicks into gear those involuntary mechanisms that lead to food cravings. This is why in any weight loss regime it is vital to get people to eat lots of low calorie but highly satiating foods, such as protein dense foods and vegetables in order to help them feel fuller, while still restricting their caloric intake at the same time as these foods are highly satiating for a low amount of calories. This decreases feeling of hunger and cravings for palatable foods. The body feels well fed and doesn’t panic as much in the caloric restriction phase. This also allows the person and their body to interact with food the way we were genetically designed (i.e. eat when hungry and stop when full). Also, these whole foods that are minimally processed were what we were genetically designed to eat. Not processed food, which was non-existent as hunter gatherers.
We were not designed to voluntarily restrict calories for “weight loss” purposes because our genetic makeup was formed in food scare environments where weight gain was the least of our worries. Our genetic makeup was designed to help us survive in food scarce environments, which is why our bodies rather gain weight than lose it (i.e. overeat on calorie dense food). It is also why the evolutionary mechanisms discussed above, kick into gear during caloric restriction. Caloric restriction used to be non-existent because finding calories used to be the main issue for humans. Now days, calories are plentiful and food is readily available. Especially food that is highly palatable and gives our brains what it is intrinsically looking for in food (to be discussed), which then leads to overeating and therefore weight gain. As these foods are not satiating and make us feel full after we overshoot our caloric intake to maintain a healthy body weight.
The more calories the body consumes overtime (due to various factors effecting caloric intake), the more weight gain occurs and the more the set point increases. Your set point increases because your body prefers to store fat over losing it. Once again, this is an evolutionary mechanism that ensured our survival as a species. The body could always do with some extra fat stores in case food became “scarce” again.
Furthermore, years of unsustainable yoyo dieting, with extreme caloric restrictions and weight fluctuations, which is all too common with obese individuals, increases the set point over time. As the body loses weight (especially if it is done rapidly) and puts it back on, it gets scared, therefore it slightly increases the set point in order to be better prepared for the next time there is “food scarcity” or “famine” (i.e. caloric restriction on a diet). This shows how highly adaptable the body is and once again how our genes are at a mismatch with our environment. These evolutionary mechanisms are still present in a world where food is readily accessible and we voluntarily have to restrict calories, which the body perceives as famine.
The slower the weight loss, the more time the set point has to change. The body doesn’t panic as much as it doesn’t think that there is a drastic “shortage” of food. Drastic weight loss such as with fad diets that highly restrict calories, doesn’t change the set point. A person has to keep the weight off long enough for it to change, which is usually unlikely due to all the evolutionary metabolic processes in place that the body ignites once a person is eating below their set point (e.g. hunger cravings, slowed metabolism). Because the weight loss was so drastic, the body will literally fight against your mind to put back on the weight.
A 05.-1kg weight loss per week, especially if a person has a lot of weight to lose (more weight = increased difficulty), doesn’t send the body into panic mode where it up-regulates all of the evolutionary mechanisms to prevent weight loss because it thinks it is starving (e.g. low energy, lowered metabolism and hunger). This means that once a person loses weight in a gradual manner, each small and incremental loss of weight actually has a change in the set point. Therefore, even if they lose 5-6 kg in 5-12 weeks, despite this being very slow, it is unlikely the body will rebound back to the original starting weight as the set point would have re-adjusted to a new point, which is 5-6kg lighter. This means that even if they may have a “binge,” they will feel full once their body takes in enough calories to bump their weight back up to their new set point, which is already 5-6kg lighter than when they started. Although it is slow, this is how weight loss should be done as it leads to lasting results.
Also, as a person gains more weight, more leptin is released from fat cells, which in turn increases leptin levels in the brain. Eventually the brain comes resistant to leptin’s signals, which leads to decreased satiety signals during food intake. This causes over eating.
Lastly, it must be noted that there are many people in the modern world who eat a lot of calorie dense, processed foods and expose themselves to an obesegenic environment on a daily basis and they don’t gain weight. One reason may be because their caloric output is so high on a daily basis due to being very active. Another reason may be because despite eating a lot of processed foods, their satiety (leptin) signals are working well and their set point makes them feel full at a relatively healthy body weight. Now this is not to say that these people will be healthy, as poor diet choices may lead to the development of other chronic health issues, however it seems that in those with a potential genetic predisposition to obesity will be more likely to gain weight and increase their set point in the context of an obesegenic environment, compared to someone who does not carry that same genetic predisposition. Those without a genetic predisposition may still gain weight as they get older because we age we become more sedentary and our metabolism slows down.
3) Whole foods vs processed foods:
When people begin to calculate the “calories in” part of the “calories in vs out” equation, they normally base it on food labels for a packaged food and Google for whole foods like fruit and vegetables.
However, this can often be extremely inaccurate, which can lead to feelings of disappointment when a person is not reaching their goals.
Firstly, this is because the amount of calories shown on a food label of a given food, have been determined by devices 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, just because you eat a food, doesn’t mean all the calories from that food are actually absorbed.
For example, 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. Processed food is less complex in its structure, therefore it is easy for digestive enzymes to break it down once consumed. These foods are also high in calories and low in nutrients, which means they take longer to fill us up and are less satiating.
Whereas when we eat whole foods (i.e. minimally processed food), 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 means that some of the calories from these foods are not absorbed and in the case of fruit and vegetables, things like unabsorbed fibre travels to the large intestine where it feeds the good bacteria. Processed food is mostly absorbed in the small intestine and nothing travels to the large intestine to feed the good bacteria in the gut, leading to an overgrowth of bad bacteria.
Furthermore, eating whole foods that are high in fibre and protein increase our satiety as mentioned above. These foods, when compared to processed foods, contain less calories per gram of food ingested and are much more nutrients dense. This makes us feel fuller and more satisfied. This is also because protein and fibre take time to digest (due to their complex chemical structures) and take up a lot of space in the gut, therefore this activates stretch receptors in our gut, which tells the body it has enough food and it can dampen hunger signals and increase satiety signals.
This is also 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.
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 amount of calories absorbed from a given food.
It is evident that measuring our caloric intake via food labels and Google can cause some unintended issues. Although it can give us ballpark figures of our caloric intake, it is often inaccurate due to the factors stated above. Despite this, some people can find calorie counting very useful for weight loss, however most people find it tedious and when people are only focussing on calories over the nutrient density of their diet, it can lead to the intake of foods that “fit their calorie/macro” intake for the day but may not be the healthiest foods. They also may not be whole-foods that help to increase satiety while taking in less calories, which in turns helps with compliance to a healthy eating plan.
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.
4) Socio-economic status:
People of lower socio-economic status have an increased risk of chronic disease and one of those diseases are obesity. This seems to be because healthy food is usually more expensive than processed food and there is a lack of education/knowledge and prioritisation around healthy eating. Also, people of lower socio economic classes tend to be more stressed and time poor (for a variety of reasons such as increased work hours, chaotic life situations and financial stress), which leads to an increased likelihood of them turning to cheap, fast, easy to prepare/buy food options that taste good and are usually calorie dense and low in nutritional value.
Lastly, increased stress and being time poor effects peoples sleep, diet choices and exercise motivation, which we know are important components of weight loss/weight gain. Increased stress and chaotic life situations can also be a reason as to why we see higher substance abuse in people of lower socioeconomic status, which can all contribute to weight as well.
5) 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 (another example is sex).
When our brains accomplish a key goal that is hard wired in us because it is essential to our survival (e.g. food intake or sex), a powerful “feel good” 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. This makes sense from an evolutionary perspective as behaviours that are essential to our survival should “feel good” in order to motivate us to do them.
In regards to food, 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 (e.g. popcorn and the movies or if you eat certain foods in front of the TV, screens may be a cue for food intake and the body increases hunger signals). This demonstrates the importance of removing food cues in any weight loss regime.
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 any type of 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 is 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. This is so we could overeat on those essential calories for our survival.
Now in the modern world, where high calorie food is so accessible, this evolutionary response leads to overeating of processed food and therefore 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 higher scientists to manufacture foods that stimulate reward centres in or 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 what drive weight gain. Everyone talks about insulin, leptin and other hormones, however the malfunctioning of these hormones are usually a downstream effect of consuming to many processed foods, which is driven by our brain.
6) Psychological factors:
Emotional eating as a result of psychological stress can be a large driver behind weight gain. As mentioned above, after ingesting processed food, we get a large dopamine spike, which is a reward chemical in our brain that can temporarily make us feel better if we are eating as a result of some deeper and underlying emotional issues, as well as stressors. Based on these mechanisms, it is no surprise that chronic stress and depression has a close correlation with obesity.
Stress is also a major contributor to consuming high calorie foods. 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. 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. Stress may sometimes inhibit appetite and decrease food intake, leading to periods of restriction and binging.
Stress increases the consumption of smoking and alcohol, which can often lead to us making poor decision around our health. It also effects our exersize and sleeping patterns which as you will see below effects our caloric intake.
Stress also usually coincides with being time poor, low energy levels and decreased motivation, which then decreases the likelihood of people preparing healthy meals for themselves and choosing healthy meal options. It also increases the likelihood of people turning to cheap, fast, palatable, easy to make, calorie dense foods.
Lastly, as people gain more weight, the more processed they tend consume in a viscous cycle, because weight gain contributes to poor mental health, low moods and decreased motivation to perform healthy behaviours.
7) Decreased sleep:
Most people don’t sleep enough. Stress, blue/artificial light exposure at night and generally poor diet and lifestyle factors are depriving us of a good nights sleep. Chronic sleep deprivation is closely correlated with all types of modern diseases, especially weight gain and obesity. It is one of the tightest correlations in the research literature. Next to caloric intake, sleep quality is the most important factor to weight loss.
When we don’t sleep, our brains get fatigued and crave energy dense food throughout the day as a “pick up.” Also, staying up late leads to an increased window for food consumption, which is why most people consume most of their daily calories via snack foods in front of the TV after dinner and before bed time.
Furthermore, impaired amounts of sleep can disrupt hormones that govern satiety and metabolic rate. Decreased sleep can also lead to craving high calorie food and decrease good decision making around food choices, especially when we are tempted.
Lastly, decreased sleep decreases our energy levels, therefore effecting our motivation to prepare and cook healthy food, exersize, as well as decreasing our ability to adequately handle our stressors. As seen above, stress increases the consumption caloric dense food.
Pharmaceutical medications are ubiquitous in our modern world due to the chronic disease epidemic. Many medications have been shown to increase appetite and effect metabolic rate, which in turn can lead to weight gain. A prime example of this is the contraceptive pill, which also causes imbalances in our microbiome.
Lowered sex hormones in times like menopause can effect cravings and decrease metabolic rate. However this tends to occur in conjunction with the factors listed above. Also, women who suffer from PMS, may have increased food cravings and increased hunger levels before their period, which usually results in the intake of highly palatable, sugary and fatty foods.
As you can see, the factors affecting our caloric intake are quite complex and multi-faceted and it is with this understanding, we can manipulate our diet and lifestyle accordingly, in order to achieve sustained weight loss. This means that in any weight loss regime, simply addressing caloric intake via the diet is not always enough. We also need to address factors that impact our caloric intake such as sleep, stress/mental health, education around healthy eating/food preparation, being time poor, eating whole-foods over processed foods to increase satiety while still decreasing calories, hormonal factors and medication use.
In part 2 of this series, I address the various elements that impact our overall caloric output.