Part 2 of this series focuses on current research into the effects of exercise on body fat.
Losing Weight Des Not Mean Too Much: Location Again
The good news is that only a 5-10% decrease in body fat is usually associated with very positive and significant changes in risk factors such as glucose tolerance and insulin sensitivity. Even better news is Phospholipid Transfer Protein Lactate Prostaglandins Prostacyclin Free Fatty Acids Leptin Adiponectin Adipsin and (ASP) Lipoprotein Lipase Free Fatty Acids TNF-ß IL-6 ADIPOCYTE that even a single bout of exercise can reduce triglyceride levels, increase HDL levels, reduce resting blood pressure, increase glucose tolerance, and reduce insulin resistance.16 It is important to take waist and hip measures from the get go because research shows that even without weight loss, exercise is an effective way to reduce VAT. Irwin et al did a large study with postmenopausal, previously sedentary women who were randomly assigned to control (no exercise) or exercise conditions. Even though the weight loss after 12 months was modest, the amount of intra-abdominal fat lost was considerable (8.5g/cm2) and it was dose-dependent. Women performing 200 minutes of exercise/ wk lost 4.2% body fat, and 6.9% VAT without changing their energy intake. However, weight loss be it from either caloric restriction or exercise is an effective way to reduce obesity in moderately obese men.17
Exercise: Getting at the Belly Fat
Here is even more good news for exercisers who tend not to lose much weight from their efforts: People who have a higher cardiorespiratory fitness (CRF) level will tend to have a lower VAT. However, individuals with a moderate to high CRF have lower waist circumferences than men with low CRFs independent of the BMI. In other words, just being in shape usually means a smaller waist (thus less risk) even at the same weight. The large decrease in risk factors with small weight loses is likely due to a preferential loss of VAT. The reduction in VAT is often associated with glucose tolerance and insulin sensitivity. Adding resistance training may further improve insulin sensitivity and an increase in muscle density.17, 18
Can Someone Be Fit and Fat?
Yes! This can be the case. The amount of VAT and fitness in someone is inversely associated. The frustration that some people have with not losing weight, especially elderly women, may be compensated for by the fact they are lowering their risk factors for many diseases and actually losing fat from the areas that really matter — those deep inside. Research shows an overweight or “fat” person who has a high CRF as measured by a treadmill test, will likely have less risk for developing type 2 diabetes than a “leaner” individual who is unfit. High levels of CRF reduce C-Reactive Protein and the cardiovascular mortality, independent of obesity. Moderately fit individuals had a lower VAT and SCAT and lower WC than individuals with a low CRF for a given BMI and WC. So, low CRF is associated with elevated CRP, and reduced fasting glucose control in women with Type 2 diabetes.19 A study by Riechman et al. (2002) found correlations of physical activity (PA) with visceral adipose tissue (VAT) and physical difficulties (PD).
Past research has shown that risk for cardiovascular disease, certain cancers, and diabetes to be associated with abdominal fat, particularly VAT. The level of physical activity from someone was inversely related with those same diseases (20). As people age, the amount of PA decreases, and the incidence of those mentioned diseases increases as does the VAT. They used computed tomography to scan for precise measures of abdominal fat in 65 women and 106 men. They found men had higher VAT and visceral percent adipose than women, but the women had higher subcutaneous and total abdominal adipose compared to the men. In women, the VAT and total adipose was significantly associated to leisure activity, while in the men the amount of occupational activity was significantly (inversely) associated with VAT.
The researchers also found the mean visceral, subcutaneous, and total adipose and VAT were all higher in those reporting PDs in both men and women. Age and gender contributed to the variance in abdominal adipose tissue but did not eliminate the associations of PAs and PDs. Finally, they found there was a threshold beyond which increased physical activity did not result in further abdominal adipose and VAT decreases. This finding supports the critical VAT threshold (CVATT) which Freedland (2004) has proposed.21
The Potential Role of Diet: Low Carb-Low Glycemic Index — the Winner Again
It seems that most of the modern day diets are pointing to multiple meals and either a low carb or low glycemic index diet. Well, it is no accident those diets seem to be working. There are scientific data and multiple physiologic mechanisms which show this to be the way to go. It all seems to boil down to the fact that carbohydrates (CHO) are the preferred source of fuel oxidization- resulting in increased fat deposition.22 The way to increase insulin sensitivity is to “push” the body into oxidizing fat in nonadipose tissue such as liver, pancreas, and skeletal muscle. Several studies have found low carbohydrate, high fat diets which are consumed more than 7 days actually induce adaptations to increase fat oxidation, reduce muscle glycogen content, and carbohydrate oxidation, even in well trained athletes, who are already at increased fat oxidation capacities.23,24 Another study by Sharman et al (2004) found that a ketogenic diet did not cause weight loss but raised the lean body mass.25 A good deal of research also supports controlling the glycemic index (GI) and glycemic load (GL). In a 12 month study on teenagers, those on a low GI diet lost more weight and had greater fat loss without regain for 6 to 12 months, compared to those on the conventional diet. In addition, insulin resistance increased in the conventional diet group and did not change with the low-GI diet group.26
Figure 2-1 (above) shows that both Physical Exercise and a low glycemic or low carb-high fat (ketogenic) diet seem to have similar effects in improving factors related to visceral adipose tissue and metabolic syndrome. Because VAT has a two-fold greater glucose uptake compared to SCAT, if you reduce glucose levels with a low GL you would lower the accumulation of glucose in VAT. Data shows glucose raises insulin which Physical Exercise- Cardiorespiratory Fitness Waist Circumference, BMI, and Body Fat% Hypertension, Diabetes, CHD, Insulin Resistance Amount of VAT, CRP, glucose levels Low Carb-Low GI/ GL Skinny on Fatness 7 stimulates 11-B-HSD1, increases active cortisol in VAT and enhances VAT accumulation. (26). In studies with rats, feeding them a diet high in sucrose compared to lab chow caused a significantly higher fat cell volume in VAT depots even though the total adipose tissue did not change, and higher insulin resistance.
Lower Glycemic Load→Lower Blood Glucose→Lower Insulin→Less 11ß-HSD1→Less Cortisol
Other studies have further shown the links between GL and C-reactive protein (CRP) a strong predictor of diabetes and coronary heart disease, and it is positively associated with insulin resistance and metabolic syndrome. Thus, diets which minimize the glucose levels in the blood seem to better in reducing VAT and factors related to metabolic syndrome and its accompanying effects.
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Mark P. Kelly has a doctorate in Exercise Physiology and Education Administration, he has specialties in kinesiology, exercise and nutritional biochemistry, weight management, and endurance athletic physiology. He was a nationally ranked duathlete, body building contest winner, trainer of professional athletes, and personal trainer for 20 years. He is a primary writer for the NFPT certification programs, a teacher in universities, and runs Principle Centered Health Human Performance Services, which specializes in assessments and corporate wellness. He can be reached at [email protected].