Slow Basal Metabolism And Fat Loss - What's The Skinny?

06/12/2016 14:16


'Playing cards' image created by Christophe Libert from

'I retain a lot of water!' and 'I've got big bones!', are just two of the 'get out of jail free' cards played by those of us trying to justify poorer than expected fat-loss results. But there are scientifically proven 'aces' that can be played, notably, the dealings of a lousy hand in the mutation lottery, which through an unfortunate genetic predisposition, can favour weight gain amongst a fattening environment. Hypometabolic and hyperphagic states through persistent metabolic adaptation from weight loss, and a plethora of other social-economical and physiological triggers, can make the achievement of a leaner physique feel like the cards are stacked heavily against you.

Could having a 'slow basal metabolism', in fact, be one of those 'aces'? Logically, this makes sense due to basal metabolic rate in most sedentary individuals yielding the largest hold on one's metabolism and remaining relatively constant in normal physiological conditions, amongst other varied facets of one's metabolism. But let's review the facts and current research, before revealing our hand on the matter.
Firstly, let's understand what constitutes 'metabolism' and whether any notable decrease in its 'basal speed' impacts our fat loss plans.
To sustain the status of your body composition, the number of calories ingested must be equal to those expended. This is an irrefutable truism in nutritional science. Your metabolic rate relates directly to how you expend calories, and this comprises three key drivers:
1: Resting Energy Expenditure (REE), often referred to as 'Basal Metabolic Rate' (BMR) or 'Resting Metabolic Rate' (RMR). Despite there being a ~10 percent difference between the two, for brevity sake, I will coalesce them.
2: The 'Thermic Effect of Feeding' (TEF).
3: Your 'Active Energy Expenditure' (AEE).
REE: This is the number of calories required to maintain basic physiological functioning such as the maintenance of the lungs, kidneys and brain; the pumping of the heart; and other essentials of bodily maintenance. REE is often measured at rest and constitutes ~60-75 percent of your energy metabolism, with fat-free mass (skeletal muscle and organ mass) being the primary beneficiary.

TEF: Is the amount of energy produced digesting and processing food. Think of the energy processes that need to occur for protein to be enzymatically broken down, transported, and released into the blood stream to contribute to protein turnover. Other key processes are required for the digestion and utilisation of fats and carbohydrates too. This constitutes ~8-10 percent to your overall metabolism.
AEE: This can be divided into two tiers - 'formal exercise thermogenesis' and 'non-exercise activity thermogenesis'.
Formal exercise thermogenesis means the calories expended through physical activity such as soccer, running and lifting weights. This expenditure can be further broken down into two sub-categories:

- Exercise expenditure: The number of calories amassed during the actual exercise.
- Post-exercise expenditure: The number of calories expended after exercise due to elevated body temperature, re-synthesis of muscle glycogen, ion distribution, ATP replenishment, and enhanced protein turnover. These 'post-exercise' processes can ensue for up to ~24-72 hours.
Non-exercise activity thermogenesis: This accounts for the calories expended due to non-formal forms of physical activity: fidgeting, adjustment of posture etc. AEE contributes ~30 percent to your overall energy expenditure, depending on the activity status of the individual.
The Research:
In a recent paper in the American Journal of Clinical Nutrition, researchers extracted basal metabolic rate data from 757 volunteers from the research database of the Mayo Clinic.  The 757 subjects' BMR were measured via indirect calorimetry, which is a measure of the ratio of oxygen consumed to carbon dioxide produced. The researchers took the top and bottom 15 percent BMRs of subjects, and observed their weight changes over the following nine years.  The differences in metabolism between the low and high subjects were ~500 kcals, which should result in the low group achieving a greater rate of weight gain in the long-term. However, the results highlighted that there was no difference in the percentage of weight change per year between the low and high BMR subjects. The research also identified subjects who achieved a 10 kg weight gain over three years, found no difference in the percentage of subjects who were either in the low or high BMR groups. They then analysed subgroups of participants with a body mass index of greater than 30 - signifying obesity - and found no significant trend in subjects' weight in relation to either having a low or high BMR. Finally, the researchers analysed smaller percentile groups of the upper 5-10 percent of lower and higher BMRs with a difference of ~600-700 Kcals between the groups. Again, the authors found no significant difference in weight gain.
What does this research suggest? It suggests that, despite a measured lower basal metabolism, there are more important independent components that can affect your weight gain or weight loss. These include energy consumption, formal exercise and non-exercise activity thermogenesis. If anything, this news should add a spring to the step for those currently perturbed that a lower basal metabolic rate will ultimately defeat a successful fat loss strategy. 

By focusing on consistent hypocaloric consumption that is geared towards maximising satiety in a manner that permits malleability, you will consistently lose weight. This, combined with a heightened level of formal and non-exercise thermogenesis - especially the latter - will accentuate your fat-loss sensibly. You must also understand that the process becomes progressively more challenging as your body gets leaner. Through evolution, your body does a wonderful job at guarding weight loss, due to a process called adaptive thermogenesis. Though, even in this scenario, AEE is the largest beneficiary of such a reduction, with a 10 percent weight reduction seeing the bulk of the slowing on REE.
Having a 'slow basal metabolism' doesn't automatically make you the joker in the weight management pack.  In fact, you are in control and you alone, are able to grasp your weight management regime by the scruff of the neck and take action. That sounds logical and straightforward, doesn't it? That's because it is. In practice, for all the reasons discussed above, it isn't always an easily attainable goal. There is no 'three card trick' to beat genetics. But we are each in control of 'playing the hand' we are dealt. Just as in other areas of life, some hands are more favourable than others. Ultimately, by consistently focusing on the 'basics' as explained above, we all have the ability to 'come up trumps' over time.