Jane has done a wonderful job of parroting some of the most popular myths about low carb diets.
Water loss: It is true the first few pounds of weight loss on a low carb diet come from water but it isn't a bad thing and I didn't lose 60 lbs of just water. Your body isn't 'depleted' of carbohydrates, you do lower your storage of glycogen and the attached water molecules. There is normally about one teaspoon of glucose in the bloodstream of the average person. All the rest is put into storage in the form of glycogen and fat. Do drink plenty of water and if you are on a very low carb plan, during the induction or intervention phase of the diet you may want to supplement magnesium and potassium, also add salt if you get light headed. These minerals are lost when you lose the water at first but supplementation probably won't be necessary after this first phase.
Constipation: Many low carb foods have plenty of fiber there are lists of low carb fruits and vegetables allowed on most low carb plans like these:
Even on a very low carb induction or intervention phase you can add ground flax or chia seeds to a salad to increase your fiber.
For the record, if you're constipated on a low carb diet consider that you may not be eating enough fat and fiber isn't all it's cracked up to be. Also, if you supplement magnesium constipation probably won't be a problem.
Ketosis: http://en.wikipedia.org/wiki/Ketosis This is a fairly detailed description of true benign dietary ketosis and the difference between it and a medical condition called diabetic ketoacidosis, which Jane seems to be confused about. Some low carb diets recommend staying in ketosis, some do not. At any rate the breath smell may be due to eating too much protein. If that seems to be a problem you can calculate your own individual protein needs based on your individual size, activity, and carbohydrate level. These needs will change during the course of the diet because the body adapts to fat burning after a few weeks, so it will need less dietary protein for conversion to glucose through gluconeogenesis.
http://www.phlaunt.com/lowcarb/DietMakeupCalc.php The main idea is to burn more fat and curb appetite through hormone manipulation rather than strictly calorie reduction and will power.
Potential loss of muscle: True, when you limit carbohydrates your liver converts protein to glucose through gluconeogenesis. If dietary protein is not adequate it will have no problem raiding muscles and organs for the protein, that is one reason why it is essential to eat adequate protein while dieting by any method. An adequate protein diet will always spare more muscle than a low protein diet.
Although more long-term studies are needed before a firm conclusion can be drawn, it appears, from most literature studied, that a VLCARB is, if anything, protective against muscle protein catabolism during energy restriction, provided that it contains adequate amounts of protein."
Calcium excretion: Bones are one of the most protein dense tissues in the body and recent research indicates that increased protein intake improves calcium absorption from food.
"In conclusion, this study did not confirm the perception that increased dietary protein results in urinary calcium loss. The constellation of findings that meat supplements containing 55 g/d protein, when exchanged for carbohydrate did not significantly increase urinary calcium excretion and were associated with higher levels of serum IGF-I and lower levels of the bone resorption marker, N-telopeptide, together with a lack of significant correlation of urinary N-telopeptide with urinary calcium excretion in the high protein group (in contrast to the low protein) point to the possibility that higher meat intake may potentially improve bone mass in many older men and women."
If you have metabolic syndrome, high fasting insulin, if you are always hungry when trying to diet, if you have 30 lbs or more to lose, if you get sleepy after meals or faint and hungry again a couple of hours later, even if you're normal or under weight but have acne, high blood pressure, reflux or abnormal cholesterol give low carb a try. Don't listen to the know-it-all know nothings of the world, like Jane. Read a couple of books like, Gary Taubes' Good Calories Bad Calories, Drs Eades' Protein Power Life Plan, or Atkins New Diet Revolution and give it a try.
We could all benefit from less sugar and other white carbs in our diets but some of us don't tolerate the healthy whole grains any better and find less hunger, more weight loss and much better health on a high nutrient, low carb diet.