Losing weight, as millions of people have discovered, is seldom easy. Maintaining the weight loss is even more difficult. However, data exist to prove that it can be done. And the reality is that it must be done, since obesity is increasing rapidly, and spreading misery in its wake.
What is obesity?
The standard definition uses the Body Mass Index (BMI) to classify weight problems.
The BMI is calculated by multiplying your weight in pounds by 703. The resulting number is then divided by the square of your height in inches.
A BMI of 18.5-24.9 is considered normal.
A BMI of 25-29.9 is considered overweight.
A BMI of 30 and higher is called obese.
Is BMI perfect?
There are several problems with the BMI. In athletes, and other people who are muscle-bound, the BMI might be in the obese range, but their body fat, which is what we are truly interested in, may well be normal. Similarly, elderly people, or those who have lost muscle mass, may have a normal BMI, but higher than normal body fat.
However, in spite of its limitations, the BMI has been found to be of practical help, and is widely accepted world-wide. Most scientific studies of obesity also use the BMI.
What other measures exist?
People also use waist circumference as an estimate of body fat.
A WHO Expert Consultation on Obesity states that a waist circumference of more than 94 cm (37 inches) in men and 80 cm (31.5 inches) in women is associated with an increased risk of metabolic complications of obesity in Caucasians. These include type 2 diabetes, cardiovascular disease, and the risk factors for cardiovascular disease.
A waist circumference of 40 inches (102 cm) in men and 35 inches (88 cm) in women is associated with a substantial increase in the risk of these metabolic complications.
These cut-off numbers are different for people of different races, such as Asians.
Body fat measurement
Several methods are described to measure body fat content. The simpler and cheaper ones are less accurate, while the more accurate ones are either cumbersome, or expensive, or both.
Skin fold thickness measurement using calipers is a simple and inexpensive, but approximate, estimate of body fat content.
The acceptable range for body fat percentage is 18-25% for men and 25-31% for women.
Burden of obesity
More than 2.1 billion people in the world are obese or overweight. This represents almost 30% of the population of the world.
According to a recent McKinsey Global Institute report, the global economic impact of obesity is approximately $ 2 trillion a year. This is close to the global costs of smoking, armed violence, war, and terrorism.
More than two-thirds of all adults and one-third of school age children in the USA are overweight or obese.
Many diseases are associated with obesity, including high blood pressure, type 2 diabetes, heart disease, lipid problems, and some cancers.
The US spent $147 billion in 2008 on diseases related to obesity. And the number of obese and overweight people keeps rising.
Clearly, we need to do more.
What does work?
Comprehensive lifestyle intervention programs which include caloric reduction, increased activity, and behavioral intervention by trained professionals have been clearly documented to be of value for weight loss.
The key component is creation of an energy deficit (calories consumed and calories burned) of about 500-750 calories a day.
The type of diet (low fat, low carbohydrate, high protein, etc.) is much less important than consuming fewer calories.
The behavioral component is also important, focusing on self-monitoring of diet (with a food diary), weight and activity levels, preferably daily. In addition, information and feedback is provided by trained interventionists, either face-to-face, or by remote means (telephone or internet).
Usual pattern
With the programs described above, weight loss of at least 5% is often seen, with the maximum weight loss usually seen by 6 months. Some people can lose even 10% of their initial weight.
This degree of weight loss (5-10% of the initial weight) has been shown to be clinically significant, and has a positive effect on several diseases associated with obesity.
Other adjuncts
Weight loss medicines, and surgery in some cases, can be employed in higher risk patients, who need to be selected and monitored carefully.
What happens next?
This is the major problem.
Weight starts to creep back up within 6 months to 1 year (in non-surgical patients). A number of people, in the absence of further intervention, may regain all of the weight they had lost. Why is that?
“The empire strikes back”
The body starts to fight.
Energy balance is crucial for the survival of animals and humans. Our bodies have developed a finely-tuned system of regulatory mechanisms which kicks in as we lose weight.
Appetite and satiety, or fullness, are controlled by signals sent by multiple hormones and peptides. These signals are received by the hypothalamus in the brain, which then controls the response by the body to weight loss.
Leptin and ghrelin
These are only two of dozens of hormones affecting energy balance and appetite.
Leptin is a hormone released by fat cells. Its site of action is the hypothalamus. It reduces appetite and leads to reduced food intake. Ghrelin is produced by the stomach and increases appetite.
Response to weight loss
Weight loss leads to significant reductions in levels of leptin, cholecystokinin, and peptide YY. There is also an increase in ghrelin levels. All of this favors appetite stimulation, and increased food intake. Interestingly, these changes can persist for 12 months. No surprise, then, that the body tries to regain the weight it had lost.
Conclusion
- Weight loss requires a negative energy balance, and most diets which reduce calories are helpful.
- There is a need for an increase in physical activity as well.
- Comprehensive behavioral intervention works best, with an emphasis on self-monitoring of diet, weight and exercise.
- Some carefully selected patients require medications and/or surgery.
- Regulatory mechanisms with hormonal changes lead to a tendency to regain the lost weight, starting at 6-12 months.
- There are methods to fight this regain of weight, as well. All is not doom and gloom. Stay tuned for a whole new discussion of weight maintenance.
Excellent article.
Thank you.
Very good article
Thanks, Gloria.
WOW, Dr. Harsh, first you started with the amount of sleep we need, now you are hitting on weight problems, both concerning me. thanks for the eye opening facts on both these subjects. thanks for the time you spend to keep us informed on things we can do to stay healthy. look forward to the next blog!
Thanks for the kind words, Emily. I feel it is important for me to give something back, and so I will try to keep putting out blogs about issues I feel are important for people to be aware of.
Cheers.
Shiv Harsh