Changes in food cravings during low-calorie and very-low-calorie diets

Objective: This study examined food cravings during a primarily food‐based low‐calorie diet (LCD) and a supplement‐based very‐LCD (VLCD). Research Methods and Procedures: The Food Craving Inventory (FCI) was used to measure general cravings and cravings for specific types of foods (sweets, high fats, carbohydrates/starches, and fast food fats). The FCI was completed by participants in the LCD and VLCD programs at baseline and after 11 weeks of dieting. The VLCD group also completed the FCI at Week 6 and after 5 weeks of a refeeding phase, when their diet consisted primarily of solid food. Results: From baseline to Week 12, craving decreases were greater for the VLCD group than for the LCD group on all measures. All craving measures decreased significantly for the VLCD group. The LCD group experienced a marginally significant decrease in sweet cravings. Within the VLCD group, all craving measures decreased significantly by Week 6 and did not change thereafter, including after resumption of solid food intake, and craving scores during all dieting points were lower than baseline. Changes in cravings were not related to weight loss. Discussion: Cravings did not increase during either diet; all changes represented decreases. Compared with a primarily food‐based diet (LCD), a more restrictive supplement‐based diet (VLCD) resulted in significantly larger decreases in food cravings that occurred by the end of the 5th week of supplement use and did not rebound with resumption of solid food intake. The results of this study suggest that food cravings diminish with calorie restriction.     

Muscle metabolism during prolonged physical exercise in dogs

In order to provide reference data, adenine nucleotide, creatine phosphate, glycogen, glycolytic intermediates and lactate muscle contents were measured in 49 dogs under resting conditions and during prolonged physical exercise of moderate intensity performed until exhaustion. Both the resting and exercise values of the measured variables were remarkably similar to those described in human subjects, except muscle lactate content which achieved higher values during submaximal exercise in dogs than in men.     

Changes in sleep patterns during prolonged stays in Antarctica

Various countries have permanent research bases in Antarctica that are manned year-round by a few members of an expedition team, facing extremes of temperature with the associated hardships. Acclimatisation to such an environment is associated with pyschophysiological changes along with alterations in sleep patterns. The present study was undertaken to explore the changes in sleep patterns of six members of the Indian expedition team during their winter stay at Maitri, the permanent research station of India in Antarctica. The mean (+/- SEM) age, height and weight of the subjects were 35.7 +/- 2.32 years, 168.3 +/- 2.37 cm and 71.0 +/- 1.88 kg, respectively. Polysomnographic sleep recordings were obtained as baseline data in November 2004 in Delhi (altitude 260 m, latitude 29 degrees N, longitude 77 degrees E); data on the same parameters were collected at Maitri, Antarctica (altitude 120 m, latitude 70 degrees 45' 39' S, longitude 11 degrees 44' 49' E) from January to December 2005. A one-way analysis of variance with repeated measures showed a significant variation with time (month effect) in most of the sleep parameters recorded. Total sleep time decreased from Delhi baseline values in all months, sleep efficiency decreased significantly during winter months, duration of waking period after sleep onset increased significantly in winter, sleep latency increased immediately after exposure in January, stages 3 and 4 (slow wave sleep) reduced during dark winter months, whereas stages 1 and 2 and rapid eye movement sleep increased during dark winter months. This study observed a prevailing general trend of sleep disturbances amongst overwintering members in a modern Antarctic station.     

Carnitine metabolism during prolonged exercise and recovery in humans

Lennon et al. (J. Appl. Physiol. 55: 489-495, 1983) have recently reported a large loss of muscle total carnitine (TC) after 40 min of moderate exercise. These authors have also suggested that elevations in plasma esterified carnitine (EC) were due to the release of these carnitine esters from muscle during exercise. After 10 male subjects underwent 90 min of cycle egometry we found no alteration in muscle TC from preexercise values. Plasma EC progressively increased above resting values during exercise and remained elevated above rest at 0.75 and 1.5 h into recovery. Elevations of plasma EC were largely due to a decrement in free carnitine (FC) in both conditions. Immediately postexercise the urinary fractional reabsorbsion of EC and FC were similar to that at rest. These results suggest that a net loss of TC from exercising muscle does not occur. As in other conditions marked by falling insulin concentrations, elevations in plasma EC could result from an exchange of carnitine with the hepatic carnitine pool.     

Changes in several lipid metabolism indices following death and resuscitation]

The lipolytic activity in the adipose tissue, unesterified fatty acids (UFA) in the blood and adipose tissue, as well as ketone bodies and beta-lipoproteins in the blood were determined in dogs during dying of acute blood loss and the restorative period after the revival of the organism. During agony the activation of lipolysis in the adipose tissue, a decrease of UFA and beta-lipoproteins and an increase of ketane bodies contents in the blood were detected. At the end of the third minute of clinical death there occurred a depression of lipolysis and an increase of UFA content in the adipose tissue. One hour after the revival of the organism the blood UFA content and beta-proteins decrease, but the ketone bodies content rises; simultaneously there occurs some reduction of lipolytic activity of the adipose tissue. At the late postreanimation period (in 1, 3, and 7 days) an activation of lipolysis in the adipose tissue and an increase of UFA, ketone bodies, and beta-lipoproteins content in the blood was noted. The adipose tissue UFA content was low during the postreanimation period. The given results have shown that the changes in the lipid metabolism could play some role in the pathogenesis of non-reversibility during dying and after the revival of the organism.     

Metabolic changes induced by combined prolonged exercise and low-calorie intake in man

Thirteen middle-aged women and 10 men walked 344 km during 7 days. The daily walking distances were 57, 53, 67, 53, 41, 36, and 37 km at an average speed of 3.5 km X h-1. During the hike the subjects drank water, mineral drinks, and juices ad libitum. Except for some natural products, no food intake was allowed. During the hike the body weight and serum protein concentration of the subjects decreased by about 7%, on average. Serum triglyceride and total cholesterol decreased drastically, about 30-40% during the hike, but HDL-cholesterol showed a tendency to increase, giving a 40% increment in HDL/total cholesterol ratio. Serum free fatty acids rose 1.5-2 times above the starting level. Serum glucose and evening insulin levels decreased significantly during the hike. Serum cortisol in evening samples after the daily walking and plasma norepinephrine concentrations were significantly increased, reflecting the immediate daily response to the combined fasting and walking. Serum testosterone levels decreased in men but not in women, indicating the involvement of the LH-testis pathway in the decrease obtained. Serum ASAT activity rose to about three times the starting level during the hike, whereas gamma-GT activity gradually decreased. These marked metabolic changes caused by combined fasting and several days exercise were in many respects (as in cholesterol, HDL/total cholesterol ratio or testosterone levels) more pronounced than those earlier reported to be caused by exercise or fasting alone.     

Alterations in basal glucose metabolism during late pregnancy in the conscious dog

We assessed basal glucose metabolism in 16 female nonpregnant (NP) and 16 late-pregnant (P) conscious, 18-h-fasted dogs that had catheters inserted into the hepatic and portal veins and femoral artery approximately 17 days before the experiment. Pregnancy resulted in lower arterial plasma insulin (11 +/- 1 and 4 +/- 1 microU/ml in NP and P, respectively, P < 0.05), but plasma glucose (5.9 +/- 0.1 and 5.6 +/- 0.1 mg/dl in NP and P, respectively) and glucagon (39 +/- 3 and 36 +/- 2 pg/ml in NP and P, respectively) were not different. Net hepatic glucose output was greater in pregnancy (42.1 +/- 3.1 and 56.7 +/- 4.0 micromol. 100 g liver(-1).min(-1) in NP and P, respectively, P < 0.05). Total net hepatic gluconeogenic substrate uptake (lactate, alanine, glycerol, and amino acids), a close estimate of the gluconeogenic rate, was not different between the groups (20.6 +/- 2.8 and 21.2 +/- 1.8 micromol. 100 g liver(-1). min(-1) in NP and P, respectively), indicating that the increment in net hepatic glucose output resulted from an increase in the contribution of glycogenolytically derived glucose. However, total glycogenolysis was not altered in pregnancy. Ketogenesis was enhanced nearly threefold by pregnancy (6.9 +/- 1.2 and 18.2 +/- 3.4 micromol. 100 g liver(-1).min(-1) in NP and P, respectively), despite equivalent net hepatic nonesterified fatty acid uptake. Thus late pregnancy in the dog is not accompanied by changes in the absolute rates of gluconeogenesis or glycogenolysis. Rather, repartitioning of the glucose released from glycogen is responsible for the increase in hepatic glucose production.