As with all things health and fitness orientated, the efficiency with which one responds to, adapts to and tolerates a caloric deficit is subjective. The efficiency with which the organs of relation to the body’s ability to subdue stress are functioning, genetics and the stimuli one has previously been subject to are all influential factors regarding the efficiency with which the body will respond to a caloric deficit. Hopefully elaborating further regarding the above mentioned will help you better comprehend some of the reason as to why such a rate may differ between individuals subject to the same caloric deficit.
Before reading further, it is important to understand that above all else, if one’s caloric intake, base metabolic rate and expenditures are not considered, fat loss at a controlled, consistent and desirable rate is not impossible but unlikely.
METABOLIC ADAPTATION:
The body seeks homeostasis. Independent as to your health and fitness orientate goals, your body will do everything in its power to adapt to the stimuli it is subject to and thus subdue the stress that has ensued proceeding the implementation of what ever fat loss method you are testing its resilience to.
When in a caloric deficit for an extended period of time, it is likely your metabolic rate will slow. This is called metabolic adaption, it is something the body resorts to in an attempt to reduce the size of the caloric deficit it is subject to, in an attempt to conserve energy, slow and ideally stop the fat loss it has recognised the stress it is under is attributed to. The rate with which one’s metabolism adapts is subjective, factors like one’s testosterone levels and vitamin D intake have been proven to reduce the rate with which it slows. Given without exogenous supplementation testosterone levels can only be influenced and are for the most part governed by one’s genetics, the duration with which an individual will remain responsive to a controlled deficit prior to having to drop calories further to compensate for the above mentioned will likely differ from individual to individual despite being subject to the same stimuli, ultimately dictating the frequency with which calories must be dropped and the duration with which such an individual can diet for prior to experiencing issues regarding sleep, appetite and performance.
HORMONES:
There are numerous hormones that have a profound influence on the efficiency with which the body is able to oxidise fat, independent as to the size of one’s caloric deficit.
The hormones of the most influence in my opinion and those I shall be speaking of in greater detail are cortisol, Testosterone, Thyroid hormone and insulin.
Insulin:
In the hierarchy of hormonal influencers for fat loss, insulin still reigns as King according to current evidence. This hormone, relative to the others, is most strongly influenced by carbohydrate intake and over consumption of food, both of which cause a detrimental increase in blood sugar. Over consuming any macronutrient whether it be carbohydrate, fat, or protein will elevate this hormone. For the average sedentary Australian that overconsumes, insulin will increase and remain high. Chronic high levels of insulin will eventually cause your body to become resistant to this hormone, meaning you will have difficulty burning fat. As such, provided the stimuli two individuals have been subject to in the past differs, their responsiveness to insulin will likely differ and thus, despite being now subject to similar stimuli, it is unlikely they will lose fat at a similar rate.
Thyroid Hormone:
Thyroid hormone, secreted from the thyroid gland, helps to manage the body’s metabolic processes including your fat burning potential. This hormone is keenly sensitive to your daily lifestyle choices and events including: sleep (how long and how deep), nutrition (types and amounts of food), stress (acute or chronic), and exercise (longer moderate intensity or shorter high intensity), etc. It influences every system in your body by sensing your internal and external environment. Unfortunately, your thyroid gland is primed to think food will at some stage be scarce. As such, when an individual has been eating significantly less than the body needs to subdue the stress it is under for an extended period of time; metabolic adaption will occur. As with insulin, should the amount of thyroid hormone one’s body is secreting have been influenced by the stimuli they have been previously subject to, their responsiveness to a deficit will likely differ.
Testosterone:
Testosterone levels are partly responsible for exacerbating the traits in men we deem as masculine, be them physical or psychological. Testosterone, coupled with oestrogen and progesterone also has an influence on the hour glass shape most women desire. There are testosterone receptors all over the male and female body and as such it has a profound influence on your state of well-being, sex-drive, lean mass, bone strength, and energy levels, to name a few. Although testosterone has a stronger influence on the male body than the female body, women with levels either too high or too low can also feel and see its negative effects. Exercise, sleep and specific micronutrients can influence one’s testosterone levels, for the most part however such levels are governed by one’s genetics. As such, provided such levels differ between individuals either male or female, the rate with which they can expect to lose fat despite being subject to the same stimuli nutrition and training wise will differ.
Cortisol
Cortisol is released from the adrenal glands in response to both physical and psychological stress in order to free energy stores to be burned. In times of stress, cortisol is vital. For example, during exercise, cortisol can be beneficial for body composition by triggering fat loss.
When stress becomes chronic, cortisol levels will become excessively elevated which leads to muscle loss, fat gain and suppressed immune function.
Cortisol also has a profound influence on insulin, testosterone, T3 and T4 levels.
The efficiency with which the body is able to suppress and subdue cortisol is largely attributed to one’s caloric intake, given insulin is cortisol’s agonist. That said however, it has been identified in a study published in the US national library of medicine ( Psychoneuroendocrinology. 2011 Aug; 36(7): 1053–1061. ) that there is a correlation between the amount of cortisol secreted when subject to stress and the FKBP5 gene.
Yet another hormone somewhat governed by one’s genetics that will dictate to a degree the difference regarding the efficiency with which two subjects can expect to lose fat comparatively despite being subject to controlled stimuli regarding nutrition, training and supplementation.
SLEEP:
It is well known that a lack of sleep can hinder one’s fat loss and science has backed this up with research.
In a study performed at the University of Chicago (2010) It was found that dieters who got adequate sleep not only lost more weight but more than half of the weight they lost was fat. When such subject slept less – 5.5hrs, one quarter of the weight lost was fat. It was also concluded that the levels of Ghrelin rose when the dieters spent only 5.5hrs in bed. It is to be noted that when ghrelin levels rise, signs and symptoms such as reduced energy expenditure, hunger stimulation and fat retention have all been shown to occur. Should the quality or duration of your sleep vary in comparison to he or she that is otherwise subject to the same stimuli, fat loss at a similar rate is unlikely.
THE TAKE HOME:
In summary, there are numerous factors governed by that which you may have been subject to in the past and your genetics to be considered before you are discouraged by the rate another is responding to the same stimuli. That is not to say such factors cannot be influenced, they can, until you are aware of such factors and take them into consideration by implementing methods that have been proven to encourage improvements regarding the above mentioned, you cannot expect to lose fat at the same rate as someone that has.