Plateaus, which happen when the scale is at a standstill for several weeks, are a common part of the weight-loss process.
The Predictable Cycle of Weight Loss
During the first few weeks of losing weight, a rapid drop in pounds is normal. When calories from food are reduced, the body gets needed energy by releasing its stores of glycogen, a type of carbohydrate found in the muscles and liver. Glycogen holds onto water, so when glycogen is burned for energy, it also releases the water—about 4 grams of water for every gram of glycogen—resulting in substantial weight loss that's mostly water.
Once the body uses up its glycogen stores, it starts to burn fat for energy. Unlike glycogen, fat does not store much water and each gram of fat releases more than twice the amount of energy (i.e., calories) than a gram of glycogen. The result is that weight loss slows down substantially. At this point, the recommended rate of weight loss is no more than an average of 2 pounds per week. Losing weight faster than this is generally a sign that amounts of lean muscle mass, which like glycogen is largely water, are being broken down for energy.
As the body's glycogen stores are replenished by increased carbohydrate intake, there is a corresponding retention of water. During this time, weight stabilizes or may temporarily increase.
Why Weight Loss Plateaus Happen
By 6 months, a weight loss plateau is likely to occur.1 While plateaus are an almost inevitable response to losing weight, the physiological reasons for why they occur is not well understood.
One area of current research involves a possible link to reduced levels of leptin, a hormone produced by fat cells that is involved in the regulation of appetite. Research has shown that weight loss causes a marked decrease in serum leptin levels, which may, in turn, increase appetite.2 A dramatic drop in leptin levels also has been associated with weight regain. 3 However, more research on leptin's role in human weight regulation is needed before conclusions can be drawn.
Metabolic processes during weight loss may also impact plateaus. Losing weight can lower metabolism since a smaller body carries less lean muscle mass and burns fewer calories to move it around. Additionally, lower calorie consumption means it takes fewer calories to digest and absorb food. Taken together, a state of energy equilibrium could result, with weight remaining steady for a period of time.
This content is reviewed regularly. Last updated December 17, 2011.
Other Science Library Topics:
1 Franz MJ. Effectiveness of weight loss and maintenance interventions in women. Curr Diab Rep. 2004 Oct;4(5):387-93.
2 Infanger D, Baldinger R, Branson R, Barbier T, Steffen R, Horber FF. Effect of significant intermediate-term weight loss on serum leptin levels and body composition in severely obese subjects. Obes Surg. 2003 Dec;13(6):879-88.
3 Erez G, Tirosh A, Rudich A, et al. Phenotypic and genetic variation in leptin as determinants of weight regain. Int J Obes (Lond). 2010 Nov 2. [Epub ahead of print].