[MUSIC] A simple way to assess body fat distribution is by measuring waist and hip circumferences by a measuring tape. A standard for the exact place of measurement is not established, but often the waist circumference is measured at the midpoint between the lower rib and the highest point of the. And the hip circumference is measured at the largest circumference above the buttocks. The measurement should be made at the end of a normal expiration. In obese people it may from a practical point of view be difficult to determine the waist circumference. Another simple way to estimate body fat distribution is to measure skinfold thicknesses at various places of the body by use of a caliper. However, only subcutaneous fat distribution can be determined by this method, and it may be practically difficult to measure skin folds at places where the skin is tightly bound. For example, at the front of the thighs. An easy and precise, but less accessible way to determine body fat distribution is by DXA scanning. DXA is short for dual-energy x-ray absorptiometry. And the principle behind DXA scanning is that x-rays are absorbed to different degrees in bone, fat, and lean tissues. The subject is laying in the DXA scanner and x-rays of two energy levels are sent through the body and absorbed depending on the composition of the tissue. A detector senses the non-absorbed x-rays and the composition of different areas of the body. For example the abdomen can be calculated. By DXA scanning the body composition can only be determined in one plane. Where for abdominals have cutaneous and visceral fat cannot be discriminated. The size of these tissues can be determined by MR, magnetic resonance, or CT computed tomography scanning. Insulin sensitivity can be defined as the sensitivity of the cells of the body to insulin. A simple measure of insulin sensitivity can be derived from fasting plasma insulin and glucose concentrations in the homeostatic model assessment of insulin resistance. In short, HOMA-IR. Fasting plasma insulin and glucose concentrations are multiplied and divided by a constant. The resulting figure is one in subjects with normal insulin sensitivity and higher in insulin resistant subjects. As HOMA-IR is derived from blood obtained in the fasting state, it mainly describes the feedback loop between liver glucose output and pancreatic insulin secretion. A more dynamic measure of insulin sensitivities obtained during an oral glucose tolerance test, in short, OGTT. The test determines the ability of the body to clear glucose from the blood stream and is a composite measure of insulin sensitivity of especially skeletal muscle cells and pancreatic insulin secretion. The subject must come to the laboratory in the morning after an overnight fast and a fasting blood sample is drawn from a cubital vein. Thereafter the subject drinks a glass of water containing 75 grams of glucose. After two hours and sometimes also at various time points before two hours blood is again drawn. Blood samples are analyzed for plasma glucose concentration to determine the glucose tolerance of the subject. If plasma glucose after two hours is below 7.8 milimolar, the subject has a normal glucose tolerance. If the concentration is between 7.8 and 11.0 milimolar, the subject has impaired glucose tolerance. A glucose concentration of 11.0 millimolar or above is diagnostic for diabetes. Blood obtained during the ODTT can also be analyzed for plasma insulin concentrations, where all the different aspects of insulin sensitivity and secretion can be analyzed as area under glucose insulin curves, the Matsuda index, and more. The peripheral insulin sensitivity can be assessed by a hyperinsulinemic isoglycemic clamp. Venus catheters are inserted for infusion of insulin and glucose as well as the sampling of plasma glucose. A primed, continuous infusion of insulin is started. And a stable plasma insulin concentration is rapidly obtained. If no glucose was infused, the plasma glucose concentration would drop as insulin stimulates glucose uptake in the cells, especially skeletal muscle cells. Therefore glucose is infused simultaneously at an arrival rate according to plasma glucose measurements every five to ten minutes to maintain the individual's fasting plasma's glucose concentration. Assuming that the hepatic glucose output is shut down by the increased plasma insulin concentration, the glucose infusion rate at steady state is a direct measure of peripheral insulin sensitivity. Energy expenditure increases during exercise, a skeletal muscle requires energy to contract, the majority of energy is spent during the exercise bout. But additional energy is combusted after the exercise bout in order to regenerate energy homeostasis. This phenomenon is called excess post-exercise oxygen consumption, and constitutes approximately 15% of the total energy expenditure in relation to an exercise bout. However the influence of physical training on energy balance is more complicated than previously thought. As compensatory mechanisms might come into play when initiating an exercise training program. If, for example, a person starts to exercise for 30 minutes per day in his or her time. This might influence the activity level during the rest of the day. Hypothetically, one could get tired during the exercise program and move less outside of the exercise sessions whereby the energy expended during exercise is absorbed and the total 24 hour energy expenditure is unchanged by the exercise program. Alternatively, one could get energetic and exercising and move more during the remainder of the day whereby the total 24 hour energy expenditure is affected more than predicted based on the energy expended during the energy expended during the exercise sessions. In a recent study we examined these mechanisms. We included healthy, sedentary, moderately overweight males, age 20 to 40 years with a body fat percentage about 25. 61 males were randomized to 12 weeks of either control, CON, moderate dose exercise training not expanding 300 kilo calories per day corresponding to approximately 30 minutes per day. All high dose exercise training, high, expending 600 kilo calories per day, corresponding to approximate 60 minutes per day. Food intake in all three groups was Ad libitum, meaning that the men could eat whatever they liked. Before and after the 12 week intervention we performed various tests and some of the men were also interviewed about their lifestyle habits and everyday life during the intervention. 8 out of the 61 men dropped out during the intervention due to lack of motivation and other things. In the remaining men, the exercise training compliance was 98%, which is excellent. The exercise training program consisted of daily endurance exercise, for example, running, bicycling, elliptical training or rowing. Three times per week, exercise sessions were rigorous, defined as about 70% of maximal oxygen uptake. For the remainder sessions, exercise intensity was self-chosen but recommended to be between 50% and 70% of maximal oxygen uptake. To verify and control exercise sessions, subjects wore heart rate monitors during all exercise sessions. Heart rate data fines were inspected by the investigators every week and feedback given to the men. The exercise training program was very effective in increasing the maximum oxygen uptake by 18% in the moderate dose training group. And by 17% in the high dose training group. During the 12 week intervention the two training groups had a modest decrease in body weight. 4% in the moderate dose training group, and 3% in the high dose training group. All subjects were dexi-scanned before and at the end of the intervention. Whereby intervention induced changes in body composition could be assessed. Post training groups showed substantial reductions in body fat. Namely, 14% in the moderate dose training group and 13% in the high dose training group. Fat free mass, probably skeletal muscle, increased significantly only in the high dose training group. No changes in body weight, fat mass, or fat free mass were seen in the control group. The training related energy expenditure, meaning how much energy is expended directly due to the exercise program, was calculated based on the heart rate files. Moreover, the actually energy balance, meaning how much energy was lost from the body over the 12-week intervention, was calculated based on the change in body composition as determined by the DEXA scans. Several assumptions have to be made in these calculations, among other things that those of one kilo of fat mass corresponds to approximately 9,400 kilocalories. When comparing the training related energy expenditure and the actual energy balance over the 12 week intervention, we found that the moderate does straining group had an 85% larger change in energy balance than expected based on the training related energy expenditure. The high dose training group changed the energy balance 20% less than expected. We find this very intriguing, as it means that the body responds to an exercise training load in an active manner, and we searched for potential mechanisms to explain this. Before, during, and at the end of the 12 week intervention, 24 hour physical activity was assessed using accelerometry. According to protocol, activity counts should be increased in the two training groups, which was also the case. Interestingly, activity accounts also tended to be increased in the moderate dose training group, when activity counts during the exercise training program were subtracted. And activity counts were not decreased outside of the training sessions in the high dose training group. Moreover, according to interviews, men in the moderate-dose training group were untroubled by the exercise load and had a positive attitude towards exercise. They also describe themselves as more energetic. Based on the larger than expected change in energy balance, activity counts, and interviews, we believe that the men in the Matrados exercise training group increased their physical activity level in areas of their everyday lives that were not related to the exercise intervention, receiving a bonus energy expenditure on top of the training-related energy expenditure. As mentioned, the high dose exercise training group changed their energy balance 20% less than expected, which potentially could be explained by an exercise induced increase in appetite and hence energy intake. We investigated appetite by visual analogue scales before and after a standard breakfast. And contrary to expectations, we found an increase in satiation and fullness in the high dose training group. We also measured plasma concentrations of various hormones known to influence appetite and surprisingly found an increased concentration of peptide YY3-36 in the high-dose training group. This hormone is secreted by the gut and known to inhibit appetite and food intake. Moreover, we measure food intake before and in the end of the intervention by three different methods. Self-reported three day food records, eight-day food delivery, and ad libitum lunch meal served in the laboratory. By none of the methods, we were able to detect a change in energy intake in any of the intervention groups. Therefore, by the methods available, we are not able to explain why the energy patterns was changed less than expected in the high dose exercise training group. There is a close association between physical inactivity and overweight. However, by the research methodology currently available to us, it is difficult to elucidate what is a hen and what is the egg. Some perspective cohort studies suggest that an increase in physical activity level is associated with a lower gain of body weight and waist circumference. Various other studies suggest that obesity induces physical inactivity. To untangle the direction of the association between physical inactivity and overweight is important in order to evaluate the potential of physical training in prevention of obesity. A detailed evaluation of physical activity level and all physical fitness is difficult in large cohort studies with many thousand people and most often, questioners are used. However, in the Aerobics Center Longitudinal Study, physical fitness was assessed objectively during a maximal treadmill exercise test. Which makes this study especially interesting. Participants in the prospective cohort study, were 4,599 men, and 724 women. 20 to 82 years of age. Participants were examined three times with a mean difference between the first and the second examination of 1.8 years and a difference of 5.7 years between the second and the third examination. Examinations included assessment of physical fitness and measurement of body weight. In order to evaluate the effect of a change in physical fitness and body weight change, the change in fitness between the first two examinations was related to the change in body weight between the first and the last examination. The mean weight change for participants with no change of physical fitness between the first and the second examination was 1.5 kilo in women and 0.6 kilo in men. Multiple linear regression modelling show that improvement in treadmill time. Meaning that physical fitness was enhanced, attenuated weight gain in both men and women. On the contrary, a decrease in treadmill time was associated with a high weight gain. Moreover, each one minute improvement in treadmill time reduced the odds of a weight gain of 5 kilo or more by 14% in men and by 9% in women. Plus according to the Aerobics Center Longitudinal Study, physical fitness appears important in attenuating age related weight gain in healthy middle aged adults. An important issue in prevention of obesity is the size of the problem. How large a weight gain do we wish to prevent? The National Health and Nutrition Examination Survey, NHANES examines each year a nationally representative sample of about 5,000 Americans, including objective measures of body weight and height. Based on data from NHANES and a longitudinal CARDIA study, hill and coworkers calculated the average 8-year weight change in young American adults and found it to be 14 to 16 pounds, which is equivalent to approximately seven kilos. Assuming that 1 pound of body weight gained represents 3,500 kilo calories, they estimated that the median of the distribution of estimated accumulation is 15 kilocalories per day and the 90% of the population is gaining 50 or fewer kilocalories per day. In theory, this implies that 90% of young adults would not gain weight, if they expended 50 or fewer kilocalories extra each day by being physically active. 50 kilocalories could be expended via a 10 minute walk during a lunch break or by playing with children for less than 10 minutes. Even if this static theoretical calculation doesn't hold entirely true in the dynamic metabolism of the body, it indicates that energy imbalance causing the obesity epidemic of today is not very large and adjust a small increase in the physical activity level of the population could be part of a solution. One thing is preventing obesity another is treatment. Numerous studies have shown that weight loss is difficult for obese people and especially to keep the weight off. Studies intervening of physical exercise alone usually induce only a minor weight loss, which is often regained within 12 months. Two classical meta-analysis from the 90s show the physical exercise for 20 to 30 minutes, 3 times per week for 10 to 30 weeks and use the weight loss of approximately 100 grams per week in overweight males and females. And later, meta-analysis of randomized clinical trials comparing an exercise only to an inactive control group show that moderate-intensity aerobic exercise programs of 6 to 12 months induce a modest reduction in body weight of approximately 1.7 kilos and small reduction in waist circumference of approximately 2 centimeters in overweight and obese adult populations. Hence, physical exercise does not seem to be very effective for treatment of obesity. Multiple explanations could exist for this among others, that overweight and obese people do not pertain to the exercise program. If you do not take the pill, it does not work. Also as explained and detailed previously, compensatory mechanisms could come into play with a body defending its energy stores. This is well-known to be the case in connection with a diet-induced weight loss. Despite everything, it is very important to be realistic about how long time it takes to combust a significant amount of calories. For example, it takes approximately 1 hour of biking or gymnastics to combust 500 kilo calories. Assuming that 1 kilo of fat contains approximately 9,400 kilo calories, one would need to bike or do gymnastics for approximately 19 hours to lose 1 kilo. It is apparent that it takes a significant amount of time to lose weight by physical exercise. However, this should not discourage overweight and obese people from exercising as physical exercise decreases both morbidity and mortality. [MUSIC]
