Man stepping onto bathroom scale while wondering about fat loss vs. weight loss

Fat Loss vs. Weight Loss: What Is the Difference?

Medically reviewed on January 5, 2024 by Jordan Stachel, M.S., RDN, CPT. To give you technically accurate, evidence-based information, content published on the Everlywell blog is reviewed by credentialed professionals with expertise in medical and bioscience fields.

Table of contents

How bodies utilize energy depends on the types of calories you consume. Eating a diet high in carbohydrates can lead to a quick spike in blood sugar levels, as carbohydrates are broken down into glucose, providing a rapid source of energy.[1]

On the other hand, a diet rich in fats can result in a slower, more sustained release of energy, as fats can be metabolized into molecules called ketones.[2] Exploring the keto diet's advantages and disadvantages is vital for those considering a high-fat, low-carbohydrate diet. Conversely, proteins primarily support the health of tissues and muscles but can be used inefficiently for energy when carbohydrates and fats are unavailable.[3]

The types of macronutrients bodies use can influence weight loss: an overall reduction in body weight, which can include body fat loss, muscle loss, and water-weight loss.

What Is Fat Loss?

If you eat more calories than your body burns in a day, the excess nutrients can be stored as fat reserves, leading to weight gain. Alternatively, body fat loss occurs when you create a calorie deficit—that is, eating fewer calories than your body requires in a day.[4]

In this case, the body accesses the fat reserves (triglycerides) for energy by breaking them down into fatty acids and glycerol. The blood disperses these components throughout the body to fuel various physiological processes, such as [5]:

  • Breathing
  • Maintaining healthy hormone levels
  • Daily movement or exercise

When fatty acids reach the muscles and tissues, via blood flow, they enter the cells’ mitochondria, where fats are effectively burned. But fat cells don’t completely disappear from the body. So, where does fat go when you lose weight? Fatty acids leave the fat cells, shrinking the cell and making the body look more lean. It may be more accurate to say that you empty fat cells, rather than burn them.[4]

When bodies lose fat, the numbers on the scale can go down.

How To Measure Fat Loss

While monitoring total weight loss and changes in body composition can hint at the loss of body fat, it isn’t the most accurate way to monitor fat loss when losing weight. Instead, people on a health journey can implement three measurement tools, detailed below, although their efficacies are up for debate as well:

  • Body fat scale – These body fat scales can estimate weight and body composition (percentages of fat, muscle, and water inside the body) using bioelectrical impedance analysis (BIA). However, studies have found that body fat scales can be inaccurate when determining a person’s body fat percentage.[6]
  • Skinfold caliper – Skinfold calipers measure skinfold thickness to estimate the total amount of fat in the body. They’re not always accurate, particularly when used improperly. It’s critical to read the instructions that come with the device for the most precise results.[7]
  • Body measuring tape – People can use a body measuring tape to measure the circumference of their waist and hips, which may hint at fat loss.
  • Dual-Energy X-ray Absorptiometry (DEXA) – This technology helps to measure body composition, specifically bone mineral density, lean tissue, and fat mass.[8]
  • Hydrostatic weighing – Weighing a person in water can help to determine body fat percentage by way of measuring body density measurements. It’s considered one of the most accurate ways to measure body fat.[9]

What Is Muscle Loss?

Muscle loss, or muscle atrophy, refers to the thinning or decline in muscle mass. Physically, your muscles will decrease in size, and you may experience [10]:

  • Weakness
  • Numbness
  • Difficulty walking and/or balancing
  • Difficulty swallowing or speaking
  • Memory loss

Someone can develop muscle atrophy if they live a sedentary life—that is, spending six or more hours a day sitting or lying down with very little physical activity or movement. Malnourishment can also cause the muscles to weaken, as can medical conditions like muscular dystrophy, Charcot-Marie-Tooth disease, stroke, and dermatomyositis.[10]

Age-related muscle atrophy, also known as sarcopenia, also affects muscle mass. While it is age-driven, a lack of physical activity and an unhealthy diet can also contribute to a reduction in muscle mass and physical abilities as one gets older.[10]

In times of starvation or extreme caloric restriction, the body can also begin breaking down muscle tissue for energy. While this process provides the body with readily available amino acids, it can also deplete muscle mass and cause weight loss.[11]

Failing to consume the recommended protein intake (1.2 grams per kilogram of body weight) can also lead to the skeletal muscles wasting away, as protein is the primary source for muscle maintenance and repair.[12]

How To Preserve Muscle Health During Weight Loss

While weight loss can provide many benefits to people who are obese and overweight, such as a reduced risk of diabetes, coronary artery disease, and obesity-related cancers, restrictive diets can lead to the loss of lean muscle mass, which may also increase one’s risk of developing sarcopenia as they age.[13]

All that said, a scientific review found that muscle mass is a poor indicator of muscle quality. For example, people who are obese likely have more muscle mass, although this does not equate to greater muscle strength. The quality of muscle tissue plays a crucial role in determining strength and is influenced by factors like [13]:

  • Muscle fiber composition
  • Neural activation
  • Overall muscle function

Interestingly, the review also uncovered that diet-induced weight loss may reduce fat content and lean muscle mass without decreasing muscle strength. However, the subject requires further research.[13]

To prevent muscle loss when losing weight, researchers recommend strength training, high-resistance exercise training, and a low-carb, high-protein diet to improve insulin sensitivity, which maintains healthy blood sugar levels and stimulates muscle protein synthesis to build muscle.[13]

What Is Water Weight?

Fluid buildup in the body’s tissues can cause water retention, or edema. For some, swelling in the legs, ankles, feet, face, and hands occurs as a result of improper hydration—the body hangs onto the water it does have to maintain equilibrium. In other cases, edema may progress after sitting down for long periods or as a result of hormonal changes during pregnancy.[14]

In addition to physical swelling, you can also experience difficulty walking, discomfort in the affected area, and weight gain. It’s important to note, however, that water retention does not cause an increase in body fat.[14]

Edema does not stand alone. Many potential causes may influence water retention in the body including [14,15]:

  • Gravity – Spending too much time in one place—whether you’re sitting or standing—can cause water to pool in the arms, legs, and feet.
  • Weakened valves – Weak valves can make it more difficult for blood to travel through your veins and return to the heart, which can cause a buildup of fluid in the legs.
  • Underlying medical conditions – Such health issues as heart failure, thyroid disease, kidney disease, lung disease, and liver disease may result in water retention.
  • Medication side effects – Drugs used to treat blood pressure levels or manage pain may cause edema.
  • Poor nutrition – Eating foods high in sodium can cause water retention since sodium binds to water molecules, causing the body to hold onto more water.
  • Pregnancy – Leg swelling during pregnancy is fairly common, since the uterus can put pressure on the blood vessels in the lower body.
  • Compromised immune system – Oftentimes, allergic reactions, infections, burns, trauma, or clots may lead to weight gain due to the effect that they have on the immune system.
  • High-carb diet – After digestion, carbohydrates live in the body as glucose. These molecules also store water, which can lead to water weight.

How To Lose Water Weight Effectively

The National Academy of Sports Medicine (NASM) recommends seven strategies for losing water weight [15]:

  1. Increase water intake – To take your body out of a state of dehydration, drink water consistently throughout the day (64 ounces daily) to avoid water retention and to trigger a flushing of excess water within the body.
  2. Lower sodium intake – Eating a low-sodium diet (no more than 2,300 milligrams of sodium daily) can reduce the risk of water retention.
  3. Increase potassium intake – Research shows that potassium can balance the salt-to-water ratio within the body, potentially reducing water retention. High-potassium foods include leafy greens, nuts, beans, dairy products, and starchy vegetables.
  4. Decrease carbohydrate intake – High carb intake can cause bloating. To avoid water retention, reduce the amount of carbs you eat daily and pay attention to what types of food cause the discomfort.
  5. Regular exercise – Daily movement helps to increase blood flow and reduce the pooling of water as well as activate sweating to shed excess water.
  6. Adopt certain medications – Speaking with a healthcare provider may be beneficial as they can address the root cause of your edema and prescribe the appropriate treatment plan.
  7. Use compression socks – Compression socks apply gentle pressure to the legs and feet to improve blood circulation and reduce swelling.

Manage Your Weight Loss Journey With Everywell

All that said, there is no difference between fat loss vs. weight loss. Fat loss is merely a type of weight loss that can occur, in addition to muscle loss and the loss of water weight.

If you’re looking to lose weight under the guidance of a licensed healthcare professional, enroll in the Everlywell online weight management program. Understanding the stages of weight loss can help in managing expectations and setting realistic goals. Through virtual, one-on-one visits, your provider can help to walk you through your health goals and lifestyle changes as well as recommend at-home tests that can provide insight into your unique health needs.

3 Stages Of Weight Loss

Why Does My Weight Fluctuate So Much?

Where Does Fat Go When You Lose Weight?


  1. Carbohydrates and blood sugar. The Nutrition Source. Published July 25, 2016. URL. Accessed January 3, 2024.
  2. Diet Review: Ketogenic diet for weight loss. The Nutrition Source. Published May 22, 2019. URL. Accessed January 3, 2024.
  3. Espinosa-Salas S. Nutrition: macronutrient intake, imbalances, and interventions. StatPearls - NCBI Bookshelf. Published August 8, 2023. URL. Accessed January 3, 2024.
  4. El-Zayat SR, Sibaii H, El-Shamy KA. Physiological process of fat loss. Bulletin of the National Research Centre. 2019;43(1). doi:10.1186/s42269-019-0238-z. URL. Accessed January 3, 2024.
  5. Metabolism and weight loss: How you burn calories. Mayo Clinic. Published October 8, 2022. URL. Accessed January 3, 2024.
  6. Franco‐Villoria M, Wright C, McColl JH, Sherriff A, Pearce MS. Assessment of adult body composition using bioelectrical impedance: comparison of researcher calculated to machine outputted values. BMJ Open. 2016;6(1):e008922. doi:10.1136/bmjopen-2015-008922. URL. Accessed January 3, 2024.
  7. Andrade JHC, Ripka WL, Heymsfield SB. Skinfold calipers: which instrument to use? Journal of Nutritional Science. 2023;12. doi:10.1017/jns.2023.58. URL. Accessed January 3, 2024.
  8. Krugh M. Dual-Energy X-Ray Absorptiometry. StatPearls - NCBI Bookshelf. Published June 5, 2023. URL. Accessed January 3, 2024.
  9. Pizzorno JE, Murray MT, Joiner-Bey H. Obesity. In: Elsevier eBooks. ; 2016:691-705. doi:10.1016/b978-0-7020-5514-0.00066-x. URL. Accessed January 3, 2024.
  10. Professional CCM. Muscle atrophy. Cleveland Clinic. Last reviewed January 21, 2022. URL. Accessed January 3, 2024.
  11. Sanvictores T. Physiology, fasting. StatPearls - NCBI Bookshelf. Published July 24, 2023. URL. Accessed January 3, 2024.
  12. Thalacker‐Mercer A, Fleet JC, Craig BΑ, Carnell NS, Campbell WW. Inadequate protein intake affects skeletal muscle transcript profiles in older humans. The American Journal of Clinical Nutrition. 2007;85(5):1344-1352. doi:10.1093/ajcn/85.5.1344. URL. Accessed January 3, 2024.
  13. Cava E, Yeat NC, Mittendorfer B. Preserving Healthy Muscle during Weight Loss. Advances in Nutrition. 2017;8(3):511-519. doi:10.3945/an.116.014506. URL. Accessed January 3, 2024.
  14. Professional CCM. Edema. Cleveland Clinic. Last reviewed May 17, 2022. URL. Accessed January 3, 2024.
  15. Mahaffey K. How to lose water weight effectively. URL. Accessed January 3, 2024.

Jordan Stachel, M.S., RDN, CPT is most fulfilled when guiding others towards making stepwise, sustainable changes that add up to big results over time. Jordan works with a wide variety of individuals, ranging in age from children to the elderly, with an assortment of concerns and clinical conditions, and has written for publications such as Innerbody. She helps individuals optimize overall health and/or manage disease states using personalized medical nutrition therapy techniques.
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