Weight loss vs. fat loss - is there a difference?

While it may seem like an insignificant difference in wording, from my perspective as a Personal Trainer and Health Coach - yes, there is a difference, primarily in the mindset of my clients.

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You know when we come down with the flu and are sicker than a dog? We don't have much of an appetite, if any at all, then get on the scale to be 'surprised' we are down 4lbs. This is an example of how anybody can lose weight if we just don’t eat. While it is true we will lose weight if we just stop eating, unfortunately, the weight we lose will be both muscle and fat. Whatever my client’s reason may be for embarking on this new adventure, understanding their mindset and knowledge of how weight fluctuates is critical.

A simple overview of how weight is measured –

what you should know before getting started:

Total body weight consists of fat mass and fat free mass. Fat mass is pretty self-explanatory, but includes essential fat and storage fat. Fat in the marrow of bones, in the heart, lungs, liver, spleen, kidneys, intestines, muscles, and lipid-rich tissues throughout the central nervous system is essential fat, whereas fat that accumulates in adipose tissue is called storage fat. Essential fat is necessary for normal bodily functioning which is why dropping too low in body fat % can result in unwanted adaptations like RED-S (formerly known as the female athlete triad where women may lose their menstrual cycle).[1]

Lean body mass differs from fat-free mass. When we take a body fat test such as Dexa, InBody, Hydrostatic, Bodpod, etc) or even when you weigh ourselves at home on a digital scale, we receive a number or percentage of LBM. Fat free mass is considered lean body mass (LBM) Please note, LBM does not indicate complete fat free mass. It contains a small percentage of fat (roughly up to 3% in men and 5% in women) within the central nervous system (brain and spinal cord), marrow of bones, and internal organs. [2] In some tests these sources of essential fat are estimated and subtracted from total body weight to obtain the fat-free mass.

Our Goal

Regardless of a weight loss or fat loss focused mindset, the game plan requires a deficit in energy in versus energy out. On our mission to weigh less on the scale or fit into smaller clothes, we want to keep lean body mass as high as possible – especially muscle. I focus on this because muscle helps the body burn more calories at rest, but a normal consequence of being in a deficit and reducing overall weight is a reduction in lean body and muscle mass. It is possible to maintain or even grow muscle in a deficit? Yes, but this is not the norm. [3,4]

During a deficit, our primary goal is to maximize fat loss (aka lypolisis) — the biological process of breaking down fat lipids and triglycerides in either the food we eat or that are already stored in our body. This mostly happens in the mitochondria of the muscles, which is why the more muscle you have, the more fat you burn. Exercise has been shown to improve lipolytic enzymes and improve mitochondria function, which is why working out helps you shed fat. [5]

Sometimes we have a rapidly approaching goal like a vacation, wedding or other big event where there may be quicker loss needed in order to meet the target date. Knowing this may create greater adaptations in our metabolism, there needs to be special consideration after the goal is reached to rebuild back calories to a more optimal place. Employing tactics like maintaining a high protein intake with help preserve lean body and muscle mass. [6]

Get nerdy resources:

1. https://www.uwhealth.org/health-wellness/red-s-syndrome-what-atheletes-need-to-know/51699

2. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3833312/

3. https://www.ncbi.nlm.nih.gov/pubmed/26817506

4. https://reference.medscape.com/medline/abstract/21558571

5. https://www.tandfonline.com/doi/pdf/10.2217/17460875.3.5.557

6. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3833312/