The Response to Exercise with Constant Energy Intake in Identical Twins

Abstract

Seven pairs of young adult male identical twins completed a negative energy balance protocol during which they exercised on cycle ergometers twice a day, 9 out of 10 days, over a period of 93 days while being kept on a constant daily energy and nutrient intake. The total energy deficit caused by exercise above tlie estimated energy cost of body weight maintenance readied 244 f 9.8 MJ (Mean f SEM).Baseline energy intake was estimated over a period of 17 days preceding the negative energy balance protocol. M e a n body weight loss was 5.0 kg (SEM = 0.6) (p < 0.001) and it was entirely accounted for by tlie loss of fat mass (p < 0.001). Fat-free mass was unchanged. Body energy losses reached 191 MJ (SEM = 24) (p < 0.001) wliicli represented about 78% of the estimated energy deficit. Subcutaneous fat loss was sliglitly more pronounced on the trunk than on the limbs as estimated from skinfolds, circumferences, and computed tomograpliy (CT). The reduction in CT-assessed abdominal visceral fat was quite striking, from 81 cm2 (SEM = 5) to 52 cm2 (SEM = 6) (p < 0.001). A t tlie same submaximal power output level, subjects oxidized more lipids than carbohydrates after tlie program as indicated by tlie changes in the respiratory exchange ratio (p 10.05). Intrapair resemblance was observed for tlie changes in body weight (p < 0.05), fat mass (P < 0.01), percent fat (p < 0.01), body energy content (p < 0.01), sum of 10 skinfolds (p < 0.01), abdominal visceral fat (p < 0.01), fasting plasma triglycerides (p < 0.05) and cliolesterol (p < 0.05), maximal oxygen uptake (p < 0.05), and respiratory exchange ratio during submaximal work (p < 0.01). We conclude that even though there were large individual differ- ences in response to the negative energy balance and exercise protocol, subjects with tlie same genotype were more alike in responses than sulljects with different genotypes particularly for, body fat, body energy, and abdominal visceral fat changes. High lipid oxidizers and low lipid oxidizers during submaximal exercise were also seen despite the fact that all subjects liad experienced tlie same exercise and nutritional conditions for about three montlis.

Association and linkage between an insulin-like growth FACTOR-1 GENE polymorphism and fat free mass in the HERITAGE Family Study

“…Several studies have shown that FM, FFM and AVF in sedentary people are partly under genetic control. 7 ± 9 Moreover, identical twin intervention studies showed that the intrapair variation in responsiveness was signi®cantly smaller than the interpair variation, 6,10 suggesting that the changes in FFM, FM, %FAT and AVF are also partly determined by genetic factors.…”

“…2 Aerobic exercise training can alter FM, FFM and AVF in humans, 3,4 and large individual differences in response have been reported. 5,6 Sex, age and pretraining level may explain some of these differences. That FM and FFM levels are partly under genetic control was shown in the Que Âbec Family Study with twins, adopted siblings and nuclear families.…”

“…11,12 Signi®cant intrapair resemblance was observed for both the AVF reductions with negative energy balance and the AVF increases with overfeeding in identical twin studies. 6,10 Although genetic factors explain a fraction of interindividual variations in body composition, little is known about the speci®c genes involved. Insulinlike growth factor-1 (IGF-1) is known for having strong anabolic effects both in vitro and in vivo.…”

Intrapair resemblance in very low calorie diet-induced weight loss in female obese identical twins

“…The ®rst study utilized overfeeding to cause weight gain in male identical twins of normal weight; 10 the second utilized exercise to cause weight loss in male identical twins with modestly elevated weight. 11 These studies 10,11 as well as postoverfeeding results 12 suggested a genetic contribution to the regulation of body weight, body fat and their determinants. Thus, there was a great similarity in changes in these variables within twin pairs despite large differences among twin pairs.…”

How much progress have we made over the last few decades?

“…Three intervention studies performed with pairs of identical twins confirmed that there was a latent and most likely inherited predisposition to gain Progress in obesity research C Bouchard adipose tissue and weight when exposed to a standard amount of excess energy 15 or to lose fat mass and weight when exposed to negative energy balance conditions. 16,17 The focus of research evolved rapidly to an emphasis on candidate genes, positional candidates, single-gene disorders, quantitative trait loci from genomic scans and DNA polymorphisms. There was intense cross talk between rodent genetic models and human clinical cases, particularly when it came to single-gene defects.…”