Weight Fluctuate

Why Does Weight Fluctuate or Stall After Bariatric Surgery?

April 21, 2021

We’ve all seen it. We work out, eat right, and step on the scale expecting rewards, and it doesn’t show a drop in weight for our efforts. Or worse, it’s actually gone up! Our daily weight fluctuations are normal. Variances in what you eat and drink or how active you are may make your weight fluctuate from 1-5 pounds per day [1].

Don’t give up. If you persevere through the fluctuations, you’ll see rewards.

Let’s get some perspective on weight fluctuations so you know when not to sweat the small changes and when to wait for the reward of lost pounds.

What Causes Weight Fluctuations?

Food and Water Intake: No matter the calorie content, all foods and beverages weigh something and, once consumed, will add to your weight for that day.

Exercise: People who recently started exercising may experience weight fluctuations as their body builds muscle. Working out causes inflammation, a normal result of muscle building, and it may cause water retention as your body adjusts its water output to accommodate the increased physical activity [2]. That means you may weigh more after a workout, but it’s temporary.

Energy Storage: If you eat more calories than your body can burn in a day, your body will store excess calories from food as glycogen and fat, future energy sources for your cells. The body stores around 500 grams of glycogen in the muscle and liver to use during exercise, which can add to your weight [3]. Fat gets stored in fat cells. Over time, continually eating too many calories causes your body fat stores to expand, resulting in weight gain.

Lack of Sleep: Studies show that chronic sleep loss may cause weight gain [4]. If you’re not getting enough sleep, your stress and hunger hormones, cortisol, and ghrelin may rise [4], or your satiety hormones (leptin) may decrease so that you feel hungry even after eating a meal [5].  This leads to food cravings, eating more, more fat storage, and extra weight.

Inflammation: Chronic inflammation can cause you to weigh more. Unlike acute inflammation, chronic inflammation is long-term and associated with chronic conditions such as heart disease, diabetes, cancer, arthritis, and bowel diseases like Crohn’s or Ulcerative colitis [1]. Chronic inflammation manifests itself as visceral fat on your body. Although there’s no specific diet for inflammation, certain foods either promote or inhibit inflammation and are linked to a lower risk for inflammatory diseases listed above.

How to Reduce Inflammation:

  • Eliminate Sugar and Flour: Reducing or eliminating sugary foods such as soda, fruit juices, sports drinks, sweets, and refined carbs or flour-based foods such as white bread and pasta can reduce inflammation. These foods also raise blood sugar levels quickly which can lead to overeating and more fat storage.
  • Increase Antioxidants: Eat more foods high in antioxidants known as polyphenols which lower inflammation. Polyphenols are found in berries, cherries, plums, red grapes, onions, turmeric, green tea, and dark green leafy vegetables like spinach and kale.
  • Exercise: Regular exercise may protect you against the conditions chronic inflammation may cause. Studies found that just 20 minutes of moderate-intensity exercise such as walking on a treadmill, can have an anti-inflammatory effect [2].

Water Retention: Water intake may lead to short-term weight fluctuations. You’ll temporarily weigh more after you drink fluids, and your weight will go down after you go to the bathroom. Excess water also may lead to feeling bloated or weighed down for a short time. That may be water retention. Here are some factors that can reduce water retention [6].

Factors that can reduce water retention:

    • Hydration: When a person does not drink enough water, their body stores water or retains it to prevent dehydration. Drinking enough water actually reduces water retention.
    • Sodium intake: Sodium, or salt, is an essential compound that regulates blood pressure and balances water levels in the body. Your body likes water and sodium to be balanced in your body. Too little salt may cause swelling (called edema), cramps, dizziness, or nausea and vomiting. Too much salt can lead to dehydration and mild water retention and a higher number on the scale. Keep your sodium intake under 2300 mg per day (2400 mg per day equals 1 teaspoon of table salt) [7]. To do that may mean cooking home and forgoing fast, convenient, and processed foods.
    • Urine and stool weight: Drinking a glass of water or eating a full meal can increase your body weight temporarily. However, your weight will go down after your body digests your food and beverages and eliminates your urine and stool. The National Institutes of Health (NIH) reports the average adult passes 128 grams of stool per day and 1.42 liters of urine [8]. If not urinating very often or your urine is dark in color, drink more water. If you’re constipated, consuming more fiber (fruits, vegetables, beans) and increasing your water and exercise will help your body eliminate excess weight from waste.

When and How to Weigh Yourself

  1. Weigh yourself first thing in the morning after you’ve gone to the bathroom and before you eat or drink. This provides a weight without clothing or food and drink adding to the result.
  2. Make sure your scale is calibrated and on a flat surface, not on carpeting.
  3. Weigh yourself the same way each time. Same time, same clothes or no clothes.
  4. Weigh once a week to see a pattern or trend in your weight. Weigh yourself more often only if it keeps you on track and doesn’t cause anxiety or stress.
  5. Stop weighing yourself if it defeats your motivation.  Look for non-scale ways to see that you’ve lost weight like clothes fitting better, more energy or better body function (no constipation, feeling lighter, no bloating or inflammation).

To stop fluctuations in weight, be as consistent as possible with your meals, portion sizes, and exercise. Keep focused on your goal and recheck your dietary habits:

Measure your portions: Have your portion sizes increased? Have you started eating more food than you realize? Measure your portions and compare them to national recommendations from databases like American Heart Association (AMA) or NIH.  

Track your intake: You may be eating more calories than you think. Track your intake on one of the many apps or websites available. Look at your patterns and eliminate 250-500 calories per day from your daily caloric intake to restart your weight loss [9].

Limit Carbs: Often our favorite foods don’t do us any favors. Low-carb choices can help you lose weight. Decrease your starches, sugary foods, and fruit to ½-1 cup per meal (15-20 grams of carbs per meal) or less than 100 grams per day to see your belly fat go away. Or try a diet that restricts carbs to 20-50 grams per day to induce ketosis and burn fat stores [9].

Eliminate snacking or grazing: Are you feeling hungry after meals? Are you eating more often or throughout the day, even when you’re not hungry? Protein and fiber provide long-term satiety you can’t get from carbohydrates. According to the Dietary Reference Intake report for macronutrients, a sedentary adult should consume 0.8 grams of protein per kilogram of body weight, or 0.36 grams per pound [9]. Plan 3-6 meals and focus on protein and high fiber foods. If your meals are balanced with enough protein and fiber, you will feel fuller and not as tempted to eat between meals.

Eliminate Caloric Drinks:  It’s easy to drink 100 to over 500 calories from sports waters, energy drinks or those delicious coffees. Look for liquid calories and remove them from your daily routine. Reserve them for special occasions.

Exercise: To reduce the fat stored in cells and lose weight, create a calorie deficit. Reduce your food intake by 500 calories per day or 3,500 calories per week may result in a loss of 1 pound of fat per week, according to MayoClinic.com [10]. Increase your activity to use extra calories stored as glycogen and fat.

Important tips to remember

  • Rethink small variances. A pound or two could just be day-to-day differences in food, fluids, or digestion.  If the changes persist or you hit a plateau, change things up to restart your weight loss.
  • Remember that if you graphed your losses, weight loss comes in steps like a staircase, not a steep slope. Some days you'll lose, or appear to gain, and on others, you won't.
  • Focus on your HABITS not the numbers on the scale. This is your new lifestyle, not a quick fix. You are more than what the scale shows.
  • Consistency is key to weight loss. Push through small changes in weight, or change your diet and exercise routine if you hit a plateau. You can reach your goal. Don’t sweat the small fluctuations, just keep going!


  1. Bhutani S, Kahn E, Tasali E, Schoeller DA. Composition of two-week change in body weight under unrestricted free-living conditions. Physiol Rep. 2017;5(13):e13336. doi:10.14814/phy2.13336
  2. Dimitrov S, Hulteng E, Hong S. Inflammation and exercise: Inhibition of monocytic intracellular TNF production by acute exercise via β2-adrenergic activation. Brain Behav Immun. 2017;61:60-68. doi:10.1016/j.bbi.2016.12.017
  3. Tardie, G DR. Glycogen replenishment after exhaustive exercise. The Sports Journal. 2020;41:1543-9518. 2020.41.I
  4. Leproult R, Van Cauter E. Role of sleep and sleep loss in hormonal release and metabolism. Endocr Dev. 2010;17:11-21. doi:10.1159/000262524
  5. Vasselli JR, Scarpace PJ, Harris RB, Banks WA. Dietary components in the development of leptin resistance. Adv Nutr. 2013;4(2):164-175. Published 2013 Mar 1. doi:10.3945/an.112.003152 How much does weight fluctuate? https://www.medicalnewstoday.com/articles/weight-fluctuation#causes-of-fluctuation
  6. How Much Does Weight Fluctuate
  7. Dietary Guidelines for Americans.
  8. Rose C, Parker A, Jefferson B, Cartmell E. The Characterization of Feces and Urine: A Review of the Literature to Inform Advanced Treatment Technology. Crit Rev Environ Sci Technol. 2015;45(17):1827-1879. doi:10.1080/10643389.2014.1000761Aim for a healthy weight. (n.d.) https://www.nhlbi.nih.gov/health/educational/lose_wt/index.htm
  9. Gershuni VM, Yan SL, Medici V. Nutritional Ketosis for Weight Management and Reversal of Metabolic Syndrome. Curr Nutr Rep. 2018;7(3):97-106. doi:10.1007/s13668-018-0235-0
  10. Dietary Reference Intakes for Protein.
  11. Counting Calories: Get Back to Weight-Loss Basics
Weight Fluctuate
Denise Carruth


Denise Carruth RD, is a bariatric dietician at the Surgical Weight Loss Center of UC Health in Aurora, CO. She works with a multidisciplinary team to assess patient readiness for bariatric surgery. She counsels bariatric candidates before their surgery to help them reach their pre-surgical weight loss goal, and assesses patients after their surgery to ensure that their diet is nutritionally adequate. Read more articles by Denise!