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Upper and Lower Limits of Weekly Fat Loss

Performance Training Personal Training

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When deciding to undertake a targeted intervention such as a deliberate fat loss phase, whether it be for performance, aesthetic, health or lifestyle reasons, the temptation is far too often to loose as much and as quickly as possible. 

We look at the absolute numbers of extremes based on what we see through social media, magazines and television for inspiration.

We hear stories of individuals losing 30lbs in only 6 weeks through “x” approach, how a celebrity “bounced back” from post-pregnancy weight gain just through this one supplement, or how an individual has transformed there life by losing half their bodyweight through an aggressive exercise regime and calorie restriction.

How do they achieve such large numbers of loss in such short periods of time? 

Is actually healthy in the short term or long term with these types of transformations?

Interestingly, have you ever noticed how these individuals more often than not, have to repeat this process later down the line once weight has been regained?

An example of too much, too soon?

In our previous insight, Effective Body Composition Changes, we outlined some of the contributors as to why individuals may have failed previously in attempts to lose fat mass. Today, we begin to look into the specifics of creating a detailed plan for a fat loss phase.

Based on all we’ve looked at so far, the question we need to answer first is, do upper and lower limits exist on how much we should actually lose per week? 

To understand why these limits may exist, we must stop looking at abstract absolute numbers (eg. I want to lose 20lbs…) and start thinking in terms of percentages against you as an individual (eg. my intention is to lose 8% body fat).

Why? Because each of us is unique to some degree in the composition of muscle, bone, stored fat, organ size, and body water that we each have. Comparing our experience and journey to someone else’s, is an endeavour likely to end in failure. It may take a significant change in nutrition, exercise and activity levels for a 55kg female to lose 3kg (5.4% weight loss) whilst a 120kg individual may see 3kg lost (2.5% weight loss) within a few weeks of dialling in some basic nutritional principles. Context matters…

Yet we must always remember, fat loss and weight loss are NOT synonymous. Whilst a change in body weight may coincide with a change in fat loss, if the goal is to optimise health and longevity, our focus needs to be on creating sustained losses that maintain muscle retention and promote long term fitness in a manner that enables an individual to still meet their target goal.

Under most circumstances a weekly weight loss target of between 0.5% and 1% bodyweight is likely to be most effective in the long term.

Why specifically these numbers?

At the upper end of limits, in going above 1% we need to factor in the following considerations…

  • Muscle Mass Matters: during a fat loss phase of training, one of key components is the maintaining of muscle mass. This requires a stimulus in the form of effective resistance training. Being in a hypocaloric state in which we are consuming less calories than we need, runs directly opposed to what we would need to build new muscle. Excess muscle mass is a luxury product. Imagine a scenario in which the body prioritised your bicep size over the functioning of the brain, heart, liver or kidneys… you wouldn’t survive the day! A calorie deficit creates an environment in which we don’t have the resources available to meet all demands. We therefore cannot afford to drop resistance training intensity and volume for a sustained period of time otherwise we have a nutritional environment that doesn’t support muscle growth and a lack of training stimulus to tell the body that muscle is still needed. The end result is a subsequent increase in the amount of muscle that we lose alongside fat mass. Losing at a rate greater than 1% or a total loss of greater the 10% body weight without a period of maintenance, greatly increases the likelihood of significant muscle loss. This is famine, not feast.
  • Decrease in Training Performance: anyone who has tried to run a fat loss diet whilst maintaining high levels of physical activity and/or exercise will have experienced the drop off in performance and increase in fatigue over time. A hypocaloric diet is by definition providing less calories than the body needs to maintain balance. Over time, the build of fatigue accumulates to a point in which greater levels of activity and performance are actually detrimental to not only training outcomes (loss of strength, muscle mass, power etc…) but can also impact health at far more basic levels.
  • Health and Immunity: continuing along the same lines, a hypocaloric state decreases the functioning of the immune system amongst other internal systems (endocrine, digestive, cardiovascular, musculoskeletal etc…). Being overly aggressive with weight loss targets per week, greater than 2% bodyweight, we are likely to encounter vitamin and mineral deficiencies in time as well as an increased likelihood of potential injury through associated fatigue mechanisms of being calorie restricted. 
  • Entering Very Low Absolute Body Fat Ranges: whether we desire for the aesthetic goal ourselves, we have all seen the magazine cover males and females with shredded six-packs, veins popping out sculpted muscles and a gleaming smile falsely displaying the message that “this could be you if only you did x/y/z”. What individuals often fail to consider is the simple fact that are these individuals healthy? Is it healthy for a male to have 5% body fat or a female to have 15%? Obtaining this levels of body fat percentage whilst likely genetically improbable for a lot of individuals, is also an incredibly high-stress environment. Hormonal systems related to our control of stress, thyroid (metabolism) and sex hormones production can become widely disrupted under these conditions. If your “Why” for obtaining these levels outweighs the potential for long term health, the risks may be worth the rewards, but for many of us, it simply is not worth the investment.
  • The Slowing of Metabolism and Reduction of Activity: time spent within a hypocaloric condition has a negative feedback loop on our metabolism. As calories are restricted, the body reduces our metabolic rate to preserve any possible unnecessary expenditure of energy. Similar to going into a power-saving mode. The longer we spend in these circumstances the greater this decrease becomes. The body is unbelievably clever in these instances, not only does it down-regulate metabolism, but we also see a subconscious decrease in non-exercise activity, we become more sedentary. As our metabolism drops and our willingness to move lessens, the scale weight begins to slow up. If we don’t understand these processes we become reactionary to the numbers not moving, decreasing calories further in an attempt to restart the loss. As a result greater hunger and fatigue ensues, and the problem exacerbates to the point in which adherence becomes more unlikely over time.
  • Fat Loss is a Stressful Process: as mentioned above, being hypocaloric disrupts the hormonal axis that controls our stress response. We see an increase in circulating hormones such as Cortisol. Cortisol decrease both the quality and quantity of sleep as well as disrupting the release of Growth Hormone, a powerful player in fat loss that is secreted during deep sleep which occurs in the early phases of our night time rest. Simply having higher levels of Cortisol within the system increases water retention within the body, this can fool many individuals into thinking that they are gaining weight due to it resting in subcutaneous layers (just below the skin) and giving the appearance of puffiness/weight gain. Without understanding the potential mechanisms, we again become reactionary to the scale numbers in spite of the fact water retention may be hiding the actual progress being made…
  • Hunger is a Powerful Driver of Behaviour: Terence MacSwiney, an Irish author, playwright and  politician died from a hunger strike lasting 73 days without food. Read that line again, 73 days… without eating anything. I will haphazard a guess that no one reading this Insight has ever truly been hungry. And yet we are all still driven by these short-term internal forces that demand we seek out our next meal. The ability to control hunger signalling is a huge influence over those who will be success or unsuccessful within a fat loss phase. Making sure that you can spread not only calories, but food amounts (through food volume vs calorie density) to ensure you remain as satiated as possible within a diet phase is an important consideration. As individuals get further and further into a diet phase, the signalling for hunger, cravings and unwanted thoughts regarding food all increase. Being overly aggressive with caloric restriction or over-extending a weight loss phase is a sure fire way to fall victim to hunger-signalling.
  • Fat Loss can be Psychologically Challenging: it’s a simple question that most of us struggle to answer truthfully, Why do we want to achieve the physique we desire? Sports Performance can be obvious one, the need to get faster, fitter, stronger. As can a requirement that is placed on us by external forces (a medical need to address an issue for example). But there seems to be a stigma placed on the internalised expectations to meet social norms of aesthetic appearance. Is it OK to want to be loose body fat to meet an aesthetic value we have? Understanding the true reason behind why you’re choosing to make a change is a vital component of the process. I’ve worked with many clients who’s “Why?” wasn’t strong enough to see them past the first few weeks before distraction took place and they lost the willpower to continue. Likewise I’ve had clients who’s “Why?” has taken them through dramatic transformations that they’ve managed to maintain over the subsequent years since. Ensure you have a motivating factor that is powerful enough to see you through the whole process.

If those are considerations for why an upper limit may exist, can we not just stay as far under this as possible and not run the risk?

At the lower limit of 0.5% body weight loss per week, we need to factor in the following considerations…

  • We need to actually observe objective change happening: firstly we have the simple issue of measurement error. if changes in scale weight are of such a small nature that we cannot differentiate between normal fluctuations in bodyweight across the day/week, from that which is actually intended loss, we have no capacity to measure change over time. We therefore have no real understanding of if we are any closer to the changes we’re aiming to make. 
  • Success breeds further success: secondly there is a motivational component to fat loss. We want to see change happening at least to some degree, to know for sure we aren’t failing in our attempt. It’s motivating to know that our efforts aren’t in vain and that we are moving towards our desired outcome. 
  • Why waste time unnecessarily?… finally we have the analogy of a individual doing 30mph on a motorway when the speed limit is 70mph… both individuals will get to the final destination eventually, but what value is there is going 30mph (<0.5% per week) when the speed limit is safe to drive at?

This is our starting point in establishing time frames for an individual and whether it is possible to safely and responsibly attain an outcome within time frame someone provides.

For those of you that has ever considered a fat loss phase, have a go at seeing the upper and lower limits of how quickly fat loss can be safely achieved.

Take your current body weight in pounds or kilograms, multiply by 0.01, record the number, and then bodyweight by 0.005 and record this number. Here is our window to work within. We can more more aggressive towards our higher end (1%) or more gradual towards our lower end (0.5%) but as we’ve outlined in this insight, there are consequences when we move too far away from these upper and lower limits.

In our next insight we will look further at how long we can expect fat loss phases to last as well as the types of safe limits we can expect to lose within any one phase.

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