I found this wonderful treasure of information accidentally right here on the Atkins website, under Phase 2, trouble shooting in OWL, a blue link called reasons your weight loss may stall. It explains very well things we are always talking about like muscle versus fat, water weight, etc. etc. As one who exercises frequently and has lost inches but not very many pounds I found this information very comforting & I hope it helps ease some of your minds as well! This is copied exactly from the Atkins Page & I think the blue links below are active and can be clicked on:
The Program: Trouble Shooting in OWL
FOUR REASONS FOR STALLED WEIGHT LOSS
Has this happened to you? You’re doing everything right and steadily losing weight on Atkins, and then suddenly progress stalls or even reverses. Don’t panic—it’s not that unusual. Here are four possible reasons why this may be happening.
Reason 1: Water Weight
Did you know your body is approximately 60 percent water, and muscles and some other tissues are closer to three-fourths H2O? For a 200-pound guy, that means you’re carrying around about 120 pounds of fluid. That water makes up the majority of your blood, and gives your cells shape and a fluid medium to bathe in. Your body works hard to maintain a delicate balance of water distribution while accounting for its intake and excretion. That system varies a couple of percent points up or down depending on a variety of factors, such as menstrual phase, fluid and electrolyte intake, plus exercise.
A 1.5 percent variation in those 120 pounds of water accounts for 1.8 pounds. So your water weight could swing nearly 4 pounds between 118.2 to 121.8 pounds depending on when you get on the scale. That’s why we highly recommend weight averaging and monitoring your weight loss trajectory over several weeks or months to get an accurate weight loss picture. This natural variation is also why we suggest that you not get hung up on weighing yourself daily.
Some people are more sensitive to fluctuations in water weight than others. When you exercise for the first time or try a new form of physical activity, the muscle fibers can become swollen and inflamed, causing a temporary water imbalance. That swelling stimulates pain receptors and contributes to the delayed onset of sore muscles, which usually peaks 12 to 48 hours after exercise. The soreness and swelling are transient, and fortunately the body remembers, so when you exercise again the inflammation and swelling are considerably less.
Reason 2: Fat Is Less Dense Than Muscle
Which weighs more: a pound of muscle or a pound of fat? That’s a trick question. Of course, a pound is a pound no matter what its makeup. But fat and muscle do have different densities, and therefore vary in volume. In other words, fat takes up more space than an equal amount of muscle. Here’s why: density equals mass divided by volume. The approximate density of muscle is 1.06 grams (g) per cubic centimeter (cc), compared to fat, which has a density of 0.9 g/cc. So given equal amounts, muscle takes up 18 percent less space than fat. That’s why two people who weigh the same can look very different, depending on how much fat and muscle each has. This is also why you should evaluate your progress by inches lost, how your clothes fit and which notch you use on your belt.
Relative density can also explain why weight loss might slow or stall if you start exercising—or increase the intensity or duration of your existing program—while doing Atkins. If you add resistance training, you might be accumulating muscle while losing body fat, which is great—but it could translate to a slower weight loss. But don’t stop the exercise. Instead, take comfort in knowing you’ll continue to lose fat and inches, since resistance training protects muscle but doesn’t impede fat loss.
Reason 3: Weight Loss Is Not Linear
Most of your body’s processes don’t proceed in a straight line. Rather, your body tends to alternate between rapid and slow phases or—in some cases—takes quantum leaps. A good example is the teenage growth spurt when kids may shoot up as much as 3 to 4 inches in one school year. Many examples, such as wound healing, blood clotting, glycogen synthesis, hormone secretion and development of atherosclerosis, also progress in a non-linear time pattern. Weight loss is no exception. The adage “two steps forward, one step back” should help you wrap your head around this idea. Regardless of some of the explanations above, a stall in weight loss could simply be the body’s natural course. In most cases, the temporary plateau or step backward will switch directions as long as long as you stay the course.
Reason 4: Approaching Your Goal Weight
As you get closer to your target weight, your body starts to defend against further weight loss. If you have 50 pounds to lose, the first 30 or 40 will tend to come off relatively easily because you’re further away from your goal weight. That last 10 to 20 pounds will usually take longer, and require more discipline, as the body senses the approach of its natural weight. The key is to be patient and let the Atkins Edge do its thing. For more on stalled weight loss, see How to Handle a Plateau.