There are conflicting views on the value of weight-loss diets. Some believe that if individuals have willpower and if they diet they can lose an unlimited amount of weight. Others believe that weight loss attempts are rarely successful and weight regain invariably occurs.

On October 19,2015, Oprah Winfrey made news by buying a 10 percent stake in Weight Watchers. A study of four diets-Atkins, Zone, South Beach, and Weight Watchers –demonstrated nearly equal weight loss of approximately 6.6 to 13 pounds pounds at approximately 12 months [Atallah et al; Circ. Cardiovasc. Outcomes; 2014; (6); 815-827]. Weight Watchers achieved the most consistent results at 12 months. These benefits were not completely sustained long term. According to psychologist and researcher Traci Mann, Weight Watcher’s business success stems from the repeat business of those who fail to maintain their weight loss. Thus Weight Watchers as a business is successful because most customers fail to maintain their weight loss.


Your weight is closely regulated by your brain, gastrointestinal tract, body fat stores, and pancreas. These organs communicate with each other by producing hormones that regulate your appetite [energy intake] and metabolic rate [energy expenditure]. Leptin is a hormone made by fat cells that inhibits hunger. Ghrelin is a hormone produced by cells in your gastrointestinal tract that stimulates hunger. Cholecystokinin is a hormone produced in the first portion of the small intestine [duodenum] that stimulates the digestion of fat and protein by releasing digestive enzymes and in addition causes direct appetite suppression in the brain. There are additional mediators of appetite that include peptide YY, insulin, pancreatic polypeptide, and glucagon-like polypeptide. During a fast or a diet with caloric restriction there is a reduction in the levels of leptin and a reduction in energy expenditure. There is also an increase in appetite and an increase in grehlin. Other effects of diet-induced weight loss include reduced levels of peptide YY and cholecystokinin. These changes can persist for twelve months [P.Sumithran et al; N Eng J Med 2011; 365; 1597-1604]. This means that an obese person on a weight reducing diet will encounter many hormonal changes that stimulate appetite and weight gain, and which persist for at least 1 year. Thus the high rate of relapse after weight loss is not surprising. There does appear to be a body-weight set point in obese persons that is difficult to change. Any successful management of obesity will require multiple long-term strategies to reverse the hormonal changes described above.

Exercise does reverse these changes for a short period of time. Hunger is suppressed during and for a short while after resistance and aerobic exercise [D. R. Broom et al; Am J Physiol. 296 (1); 2009; 29-35]. In addition ghrelin is suppressed during resistance and aerobic exercise and peptide YY is increased during and after aerobic exercise. The decrease in grehlin and the increase in peptide YY will result a decrease in hunger and calorie intake. These changes are transient and thus for exercise to be effective in weight loss management it must be repeated frequently and at a relatively high intensity level [approximately 60% maximal]. Resistance exercise that builds muscle will increase your resting energy expenditure-the number of calories you burn at rest and thus will help maintain your body fat loss.

A diet in which 30% of the total calories are from protein will cause rapid weight loss and a decrease in appetite and body fat [D.S. Weigle et al; Am J Clin Nutr; 2005 82 (1);41-48]. The mechanism of action appears to be the ability of protein to cause greater satiety than carbohydrates or fat. In regard to leptin blood levels the data support a decrease in the leptin“pulse”[peak minus nadir] and an increase in leptin sensitivity in the brain. Thus a high protein diet [30% of calories] is important in maintaining the fat loss of a successful diet.


Ketones are products that are made when your body uses your body fat as a primary source of energy. Normally your body uses primarily carbohydrates from your diet as an energy source and does not produce large amounts of ketones. A diet high in protein and very low in carbohydrates will often produce ketones that can be measured in your urine and blood. A ketogenic diet is an effective diet for weight loss since it reduces appetite as well as calorie intake [A.M.Johnstone et al; Am J Clin Nutr 87(1); 2008; 44-55]. These ketogenic diets have not been well studied as long-term diets nor studied in combination with vigorous resistance exercise. There is concern that bodybuilders may not benefit from ketogenic diets because low carbohydrate diets deplete muscle and liver glycogen stores and could lead to increased muscle fatigue and muscle loss.

What limited data available suggests that aerobic exercise is not hampered by a ketogenic diet. Without calorie restriction aerobic endurance exercise by well-trained cyclists was not compromised by four weeks of ketosis [S.D.Phinney et al; Metabolism 1983 32(8); 769-776].

These data suggest that long-term weight loss is possible with the combination of exercise and a high protein diet as part of your new healthy life style. The most important aspect of maintaining your weight loss is the realization that this is a never-ending life style.