1.
Intermittent Hypoxia/Hyperoxia Versus Intermittent Hypoxia/Normoxia: Comparative Study in Prediabetes.
Serebrovska, TV, Grib, ON, Portnichenko, VI, Serebrovska, ZO, Egorov, E, Shatylo, VB
High altitude medicine & biology. 2019;(4):383-391
Abstract
Background: Intermittent hypoxia/normoxia training (IHT) is considered a possible means to alleviate chronic diseases such as diabetes. In the last decade, another method of intermittent hypoxia/hyperoxia training (IHHT) began to enter the clinical practice, when the periods of breathing with atmospheric air are replaced by breathing a hyperoxic mixture. The present study compared the impact of adaptation to IHHT versus IHT on some metabolic variables in prediabetic patients. Methods: A placebo-controlled trial included 55 patients with prediabetes, sea level residents, ages 51-74 years. Control Group (16 patients) took sham 3-week course, and the IHHT Group (17 patients) and IHT Group (22 patients) received similar actual sessions of IHHT or IHT five times a week for 3 weeks, each session consisting four cycles of 5 minutes of hypoxia (12% O2) followed by 3 minutes of hyperoxia (IHHT, 33% O2) or 5 minutes of normoxia (IHT, breathing room air). Fasting glucose, oral glucose tolerance test (OGTT), blood lipids, and the level of blood oxygen saturation (SpO2) were investigated at baseline, as well as 1 day and 1 month after IHHT/IHT termination. Results: The study showed the same positive effect of two types of training: equal reduction of serum glucose concentrations, both fasting and 2 hours of OGTT; decreased total blood cholesterol and low-density lipoproteins; and an equally smaller drop in SpO2 during acute hypoxic test (breathing with 12% O2 for 20 minutes). Improved parameters persisted 1 month after training termination in both groups. Conclusion: One of the advantages of IHHT over IHT observed in this study could be some reduction in the duration of the sessions due to shortening reoxygenation periods. Further studies are required to search for additional beneficial effects of IHHT when using other training modes or other pathologies.
2.
Rationale for novel intermittent dieting strategies to attenuate adaptive responses to energy restriction.
Sainsbury, A, Wood, RE, Seimon, RV, Hills, AP, King, NA, Gibson, AA, Byrne, NM
Obesity reviews : an official journal of the International Association for the Study of Obesity. 2018;:47-60
Abstract
Eating patterns involving intermittent energy restriction (IER) include 'intermittent fasting' where energy intake is severely restricted for several 'fasting' days per week, with 'refeeding' days (involving greater energy intake than during fasting days) at other times. Intermittent fasting does not improve weight loss compared to continuous energy restriction (CER), where energy intake is restricted every day. We hypothesize that weight loss from IER could be improved if refeeding phases involved restoration of energy balance (i.e. not ongoing energy restriction, as during intermittent fasting). There is some evidence in adults with overweight or obesity showing that maintenance of a lower weight may attenuate (completely or partially) some of the adaptive responses to energy restriction that oppose ongoing weight loss. Other studies show some adaptive responses persist unabated for years after weight loss. Only five randomized controlled trials in adults with overweight or obesity have compared CER with IER interventions that achieved energy balance (or absence of energy restriction) during refeeding phases. Two reported greater weight loss than CER, whereas three reported similar weight loss between interventions. While inconclusive, it is possible that achieving energy balance (i.e. avoiding energy restriction or energy excess) during refeeding phases may be important in realizing the potential of IER.
3.
Ramadan and sport: minimizing effects upon the observant athlete.
Shephard, RJ
Sports medicine (Auckland, N.Z.). 2013;(12):1217-41
Abstract
The intermittent fasting of Ramadan could affect various aspects of body physiology and biochemistry important to athletic success. Much of the available information on this subject has been collected from sedentary subjects or low-level competitors, often without well matched controls. Other issues requiring clearer definition include the duration of fasting, the local environment, the timing of observations, and changes in training, diet and sleep patterns. Sleep may be shortened or made good with daytime naps. Circadian rhythms of temperature, metabolism, hormonal secretions and physical performance may be disrupted and incidental activities curtailed. Disturbances of psychomotor performance include daytime sleepiness, impaired vigilance and slower reactions. Food intake is limited to night-time meals. Sedentary individuals sometimes exploit Ramadan to reduce body fat stores. Well disciplined athletes usually maintain energy balance unless daily energy expenditures are very high. Protein intake must allow for gluconeogenesis, and provide quality protein ingested around training times. Blood sugar levels are likely to fall over a long and active day, even if morning glycogen reserves are maximized. Metabolism of fat should be encouraged, beginning prior to Ramadan; inclusion of fat in the pre-dawn meal also slows gastric emptying. Daytime fluid depletion is inevitable if athletes exercise in the heat, but the immediate deficit can usually be made good at night. Some studies show an initial fluid depletion, with recovery as Ramadan continues, possibly reflecting changes in urine and sweat production. Top athletes can maintain training throughout Ramadan, although coaches sometimes reduce demands through a pre-competitive tapering of effort. Late night or early morning training requires negotiation with players who are not observing Ramadan, and dietary adjustments to maintain optimal plasma amino acid levels when training. Performance of repeated anaerobic exercise is impaired, but aerobic power and muscular strength show little change during Ramadan. Ratings of fatigue are increased, and vigilance and reaction times are impaired, particularly during the afternoon. Medical issues during Ramadan are few. Athletes with diabetes mellitus should seek a medical exemption from fasting, and prescribed drug schedules should be carefully maintained. There is no major increase of injury rates, but competitors may have difficulty in producing urine for doping controls. Logical measures to minimize the effects of Ramadan include the optimization of mood state, maintenance of training, minimization of sleep loss, appropriate adjustments of diet, and the monitoring of competitors for chronic dehydration. Future research should concentrate on the changes observed in top athletes, particularly women, with data collected in the late afternoon after a known period of fasting in a well defined environment. It will be important to ensure that the lifestyle of those studied has been optimized. Implications of chronic dehydration for doping control also merit further investigation. Current data suggest that the impact of Ramadan upon athletic performance is small relative to the precision of test procedures, although it may be sufficient to cause a loss of medals. Negative effects vary widely with the type of sport, the season when fasting is observed, the local culture and the discipline exercised by the athlete.