It is an open secret that obese people who wish to lose weight need to keep to a strict healthy diet and do regular physical exercises. A new study by the University of Pittsburgh reveals that people need to exercise a lot more than once recommended.
The study, led by John M. Jakicic, was conducted on the base of the experiment involving 201 women who either suffered from excessive weight or wished to lose up to ten percent of their weight. Each of the test women participated in the research for two years.
All the women in the group were allowed to eat up to 1,500 calories a day. The group was then split into smaller groups which varied according to the amount of calories burned during physical activities every week (1,000 versus 2,000 calories a week) and the intensity of physical exercises.
After six months of the experiment, the women in each group lost about eight or ten percent of their weight. Most of the women gained weight again. When the two-year study finished, they had maintained an average weight loss of only five percent of their initial weight. There was no group that could boast of better results.
As a rule, specialists recommend to exercise for 30 minutes five days a week, which makes 150 minutes of exercises in one week. When the women participating in the research exercised for 257 minutes, or 55 minutes five days a week, they were able to maintain their average weight loss.
With use, muscles consume energy derived from both fat and glycogen. Due to the large size of leg muscles walking, running, and cycling are the most effective means of exercise to reduce body fat.
A meta-analysis of 43 randomized controlled trials by the Cochrane Collaboration found that exercising alone led to limited weight loss. In combination with diet, however, it resulted in a 1 kilogram weight loss over dieting alone. A 1.5 kilogram loss was observed with a greater degree of exercise. Even though exercise as carried out in the general population has only modest effects a dose response curve is found and very intense exercise can lead to substantial weight loss. During 20 weeks of basic military training with no dietary restriction obese military recruit lost 12.5 kg.
Diets to promote weight loss are generally divided into four categories low-calorie, low-fat, low-carbohydrate, and very low calorie.
Low calorie diets usually produce an energy deficit of 500–1000 calories per day, which can result in a 0.5 kilogram weight loss per week. They include the DASH diet and Weight Watchers among others. The National Institutes of Health reviewed 34 randomized controlled trials to determine the effectiveness of low-calorie diets. They found that these diet lowered total body mass by 8% over 3-12 months.
Low fat diets involve the reduction of the percentage of fat in ones diet. Calorie consumption is reduced but not purposely so. Diets of this type include NCEP Step I and II. A meta-analysis of 16 trials of 2–12 months duration found that low-fat diets resulted in weight loss of 3.2 kg over eating as normal.
Low carbohydrate diets are relatively high in fat and protein. They are very popular in the press however are not recommenced by the American Heart Association. Diets of this type include Atkins and Protein Power. A review of 94 trials found that weight loss was associated with decreased calorie consumption rather than any special properties of reduced carbohydrate consumption. No adverse affect from low carbohydrate diets were detected.
A further meta-analysis of 6 randomized controlled trials found no difference between the main diet types (low calorie, low carbohydrate, and low fat), with a 2–4 kilogram weight loss in all studies.
Very low calorie diets maintain protein intake while limiting calories from both fat and carbohydrates. They subject the body to starvation and produce average weekly weight loss of 1.5–2.5 kilograms. These diets are not recommended for general use as they are associated with adverse side effect such as loss of lean muscle mass, increased risks of gout, and electrolyte imbalances. People attempting these diets must be monitored closely by a physician to prevent complications.