While a pooched out lower tummy may be a fashion hazard, it's not considered a health hazard, since it is generally due to subcutaneous fat, or fat just below the surface. However, fat in your middle, evidenced by an increased waistline, is generally visceral fat, that is, deeper fat that surrounds your organs. This is the fat associated with health risks such as Type 2 diabetes and other metabolic disorders that can lead to heart attack and stroke. On whether diet or exercise is best at reducing visceral fat, the jury is still out, so you should probably do both.
Visceral or Subcutaneous Fat
Many people, including physicians, consider body mass index, which is a relationship of weight to height, as the deciding factor for obesity. However, especially in men and women over 50, a better health-risk indicator may be the waist-to-hip ratio, because it predicts the amount of visceral fat. Divide the measurement of your waist at its narrowest point by your hips at their widest point. A result of 0.95 or more for men under 60 is considered obese, while women of the same age are considered obese with a result of 0.86 or more. If you're over 60, the numbers increase to 1.03 and 0.90, respectively.
Numerous studies have been conducted on the effects of exercise on visceral fat. One study published in the "Journal of Applied Physiology" in 2005 found that what it termed "moderate" exercise, walking at a moderate pace for about 11 miles per week for six months, prevented gains in visceral fat, while just a modest increase to 12 miles per week or increasing the intensity to jogging instead of walking, resulted in a decrease in visceral fat, even when the study subjects -- both men and women -- made no changes to their diets. However, those who did no cardio exercise during those six months gained visceral fat.
Another study published in "Diabetes Care" in 2002 studied fat loss in premenopausal women through either diet alone, diet and aerobic exercise or diet and resistance training. According to that study, all three groups experienced reduction in their overall body fat levels -- subcutaneous, visceral and intermuscular -- and also improvements in their fasting blood sugar, total and LDL cholesterol levels and lipoproteins. The conclusion was that weight loss, no matter how it was accomplished, diminished visceral fat and concurrent risk factors. There was even a study in 2011 on the effects of green tea extract on visceral fat. The experiment, conducted on rats, determined that the extract did reduce visceral fat even in rats with high-fat diets. However, the downside for those who want a no-diet, no-exercise fix is that the effective dosage also inhibited protein digestion.
While results on whether diet or exercise is most effective in reducing visceral fat appear inconclusive, all results point to an overall loss of fat leading to a loss of visceral fat that, in turn, reduces certain health risks. Given that it can be difficult to lose weight by cutting calories alone without sacrificing nutrition, and that cardio and resistance training provide other benefits like stronger bones and mood elevation, to name a couple, and that without resistance training a weight loss plan can lead to muscle loss as well, it seems that the best approach is the one recommended by the American College of Sports Medicine, the Centers for Disease Control, the American Heart Association and others: Maintain a healthy diet with no more than 20 to 35 percent of your daily calories coming from fat; get at least 150 minutes of moderate activity per week to maintain your fat level and 300 minutes of moderate or 150 minutes of vigorous activity to lose fat and engage in strength training at least twice per week.
- MayoClinic.com: Body Fat in Women: Taking -- and Keeping -- It Off
- Harvard Health Publications: Abdominal Fat and What to Do About It
- Journal of Applied Physiology: Inactivity, Exercise and Visceral Fat
- Duke Health.org: Physical Inactivity Rapidly Increases Visceral Fat; Exercise Can Reverse Accumulation
- Diabetes Care:Effects of an energy-restrictive diet with or without exercise on abdominal fat, intermuscular fat, and metabolic risk factors in obese women.
- Nutrition Research Reviews: Green Tea Aqueous Extract Reduces Visceral Fat...
- CDC: Dietary Fat
- Personal Fitness Training: Theory & Practice; Mary Yoke, MS
- Photo Credit Creatas Images/Creatas/Getty Images