Whereas the ‘’calories in’’ component is an easy concept since it simply refers to the calories that a person consumes through their diet and the ‘’calories out’’ component is governed by a bunch of different factors.
The primary contributor to total energy expenditure (TEE) is resting metabolic rate (RMR), which is the amount of energy required by the body to perform basic functions (e.g., heart beating, breathing, etc.) at rest without our intervention or need to think about.
The other main component of TEE is the non-resting energy expenditure, which comprises three parts: non-exercise activity thermogenesis (NEAT), exercise activity thermogenesis (EAT), and diet-induced thermogenesis (DIT), also known as the thermic effect of food (TEF).
TEF represents the metabolic cost of processing the macronutrients (digestion and assimilation) and where RMR remains relatively unchanged.
On the other hand, NEAT and EAT vary widely within and across individuals.
NEAT encompasses the energy expenditure of occupation, leisure, basic activities of daily living, and unconscious bodily movements (spontaneous action such as fidgeting). At the same time, EAT is voluntary participation in any form of organized physical activity.
However, tilting the balance of energy in the human body in one direction, in other words going on a calorie surplus or energy deficit, can have severe physiological implications. The purpose of these mechanisms aims to keep revert the balance to its original state. As a result, getting to the right CICO balance and maintaining it is much more complex than it sounds.
Energy Balance and Its Implications: A Rather Complex Equilibrium
The shift of the energy balance towards a lower energy intake relative to the total energy expenditure is not something that should be taken lightly since it can have a host of distinct biological adaptations, including decreased RMR, reduced NEAT, and altered levels of circulating hormones that regulate appetite (increased levels of orexigenic or hunger hormones such as ghrelin and reduced levels of anorexigenic or satiating hormones such as leptin), known to influence weight loss but even more importantly long-term weight maintenance
Apart from the physiological effects, it can also have psychological consequences, which can result in a more negative relationship with food (e.g., overeating, binge eating) and body image as well as eventually lead to weight loss failure or, even worse, gaining the weight back and an ineffective weight loss cycle.
Therefore, when someone decides to enter a weight loss program, they are highly recommended to address a certified nutrition specialist who can guide them through correct dietetic practices, taking into account the physiological and psychological aspects of such a process.
Some of these dietetic practices include but are not limited to, eating balanced and nutrient-dense meals in both macronutrients and micronutrients, practicing portion control, food journaling, setting realistic weight loss goals, identifying the signals of hunger and satiety, and uncoupling highly stressful or emotionally charged situations from dietary behaviors.
The most powerful biological adaptations that occur during weight loss and operate against its continuum are the decrease in RMR and the increase in skeletal muscle activity efficiency, especially during low levels of exercise (previously referred to as NEAT).
Since these adaptations account for a 10-15% decline in TEE beyond that predicted based on body composition changes (decrease in lean mass and fat mass), they could, to a great extent, justify the high tendency to regain weight after weight loss. These adaptations are collectively referred to as adaptive thermogenesis (AT).
Specifically, AT is a natural protective mechanism allowing survival from prolonged negative energy balance by lowering overall cellular metabolic activity to preserve energy. In other words, the cells in your body, and especially your skeletal muscle cells, burn fewer calories for their activities (mainly NEAT-type activities) per unit of weight compared to what they would normally do, given the hypocaloric environment did not exist.
Overall, the abovementioned changes are the principal causes of weight loss plateau and complete or partial weight regain. Research has shown that weight loss tends to reach a plateau, ranging between 5 and 8.5kg (5-9% initial body weight) after six months, gradually increasing to 3-5kg (3-6% initial body weight) after 48 months.
In a meta-analysis of 29 long-term weight loss studies, more than half of the lost weight was regained within two years, and by five years, more than 80% of the lost weight was regained.
All of the above signifies the vulnerability of the energy balance and how altering one side of this equation eventually triggers an inverse response on the other side of the equation. As a result, despite creating the required calorie deficit, the body’s ability to lose more weight becomes exponentially more challenging, especially when the equation is violently or improperly disrupted.
For example, for a previously obese individual whose TEE was 2200kcal and thus an energy intake of 1700kcal resulted in weight loss, due to the operation of these potent metabolic and neuroendocrine adaptations, the current TEE could have dropped to 1800kcal, hence the initial calorie deficit may be almost eliminated.
One of the most typical examples of this erratic disruption is the very-low-calorie diets (VLCDs), which are implemented by extreme dieters who avidly search the web for magic diets or by self-declared nutritionists who pledge to hold the secret to permanent weight loss.
These types of diets, which typically contain less than 800 calories, should not be recommended since they can lead to increased satiety, high losses of muscle mass (the main factor that accounts for the magnitude of RMR), and thus further decreased RMR and even nutritional deficiencies if followed for extended periods.
A booming example of the unsustainability and rather the inadequacy of such diets is ‘’The Biggest Loser’’ reality television show. The obese contestants who participated in this show went through very intensive dieting. Although they lost an astonishing amount of weight in 7 months (239 pounds in one case), after six years, all of them had regained much, if not all, of the weight they lost, and some were even heavier. The participants’ energy expenditure data and the need to consistently increase their physical activity levels partly provided the answer to this discouraging outcome.
This example not only certifies how hard the body fights back against weight loss but this fight is even intensified through such extreme dietetic practices.
Could Exercise be the Key to Success?
Overall, a sustainable weight loss program is a rather difficult equation that needs to take into account a lot of variables, and although an adequate energy restriction is the most salient one, it’s not sufficient for long-term weight loss results, as stated above.
So, even though someone may be in a calorie deficit and hit their macronutrient goals (there is no significant difference between diets’ prescriptions with different macronutrient compositions as long as a healthy balanced diet with sufficient protein intake and various foods from all food groups is followed). After some time, when the adaptive mechanisms have started to kick in, this endeavor may be circumvented.
Research has shown that combining dietary modification and exercise is the most effective approach to counter these adaptive mechanisms and achieve long-term weight loss.
Could exercise arise as manna from heaven and facilitate weight loss?
Two meta-analyses demonstrated that an extra weight loss of about 1.3kg and 1.8kg, respectively, was achieved with exercise associated with a diet intervention after a 24-month follow-up period.
However, it seems that high levels of exercise beyond the proposed physical activity recommendations (150 minutes of moderate-intensity aerobic physical activity or 60 minutes of aerobic vigorous-intensity physical activity, combined with 2 days of muscle-strengthening activities) are required for continuing weight loss and even more critical for long-term maintenance of lost weight.
Especially for this group of people who struggle with weight loss and weight maintenance, the combination of resistance and endurance training is the most effective exercise prescription for long-term fat mass reduction, muscle mass maintenance, and minimized adverse metabolic adaptations fighting against weight loss and weight maintenance.
The Link That Ties Them All Together
Therefore, someone who has secured all the variables mentioned above has definitely laid the foundation for a sustainable and successful weight loss program.
However, there is a saying, “The best is the enemy of the good.”
That ‘’best’’ is very often neglected by people who try to lose weight and think that they check all the boxes, are proper sleep and stress management.
To begin with, highly stressed individuals have fewer possibilities for a successful weight loss outcome and higher rates of dropouts.
Moreover, there has been a clear association between stress levels and emotional eating, especially a higher intake of highly palatable and energy-rich foods, such as sweets.
What’s really intriguing about this association is that chronic stress and its subsequent excessive energy intake preferentially promotes visceral abdominal fatness through complex neuroendocrine mechanisms such as increased cortisol secretion.
This is really alarming considering that abdominal obesity is tightly related to chronic diseases such as cardiovascular disease and type ΙΙ diabetes.
Along with stress, sleep deprivation, and poor sleep quality have also been associated with increased energy intake and weight gain.
The mechanisms behind this association may, to some extent, be explained by changes in appetite-regulating hormones, like leptin and ghrelin, and a following lower satiating effect of foods as well as a tendency to ingest energy-dense foods.
Hence, it seems that sleep and stress exert similar effects on energy intake and that one can exacerbate the other, resulting in cumulative adverse effects on weight regulation.
The Four Pillars of a Successful and Sustainable Weight Loss Program
To put all the above into perspective, a weight-loss effort is anything but an easy process.
Many obstacles must be overcome along the way, and someone must be determined to succeed.
However, there are some basic criteria that, if fulfilled, this endeavor can become much easier and more enjoyable.
These criteria appertain to the four pillars of a successful and sustainable weight loss program which are:
- An adequate calorie deficit will lead to a slow-to-medium weight loss rate and will be under no circumstances severe (VLCD).
- A sufficient protein intake through a healthy balanced diet, irrespective of definite macronutrient ratios.
- High levels of physical activity, with greater emphasis on a resistance training program along with moderate amounts of endurance training.
- Stress management and optimization of sleep for the ultimate effect.
We should always keep in mind that there is no such thing as “the best diet.” The best diet for every one of us is a diet tailored to our personal preferences that we can follow for an extended period without necessarily counting calories or limiting portion sizes daily. People need to think about nutrition and weight loss as a lifestyle change versus a quick fix through some sort of fad/crash diet.
Overall, weight loss and even more weight maintenance can be very difficult to attain, given the complexity of energy balance and its backstage mechanisms.
So, is there a way someone could know whether they are heading in the right direction with their weight loss goals?
The answer is yes.
Indirect calorimetry (IC) is the gold standard for measuring energy expenditure and should be encouraged as a strategy to optimize calorie prescription despite energy expenditure variations.
Through IC someone can know where exactly their energy balance tilts and adjust their calorie intake accordingly.
As a result, weight loss and weight maintenance can be greatly facilitated since however hard the body fights against weight loss, IC will not lie and will give you reliable results regarding where your energy balance lies.
Subsequently, this information will contribute to a personalized and goal-oriented nutrition prescription that will at any time be in line with the actual energy needs of the individual.