Weight lifters (WL) attempt to achieve a low body fat while maintaining fat free mass (FFM) and muscle function. Body composition and isometric muscular endurance were tested in 19 experienced male WL at the end of a weight maintenance and exercise routine standardization week. The subjects were assigned to either a control (C), moderate-protein (0.8 g.kg-1.d-1), high-carbohydrate hypoenergy diet (MP/HC), or high-protein (1.6 g.kg-1.d-1), moderate-carbohydrate hypoenergy diet (HP/MC). Both hypoenergy diets provided 75.3 kJ (18 kcal).kg-1.d-1. Apparent nitrogen balance (NBAL) was assessed using nitrogen in the diet, urine, and sweat. Body fat and FFM loss via hydrostatic weighing were not different between the hypoenergy groups. However, lean body mass (LBM) change as assessed by NBAL showed that the MP/HC group had an average negative NBAL of -3.19 g.d-1 while the HP/MC group had a positive NBAL of 4.13 g.d-1. Macronutrient mix did not affect biceps endurance, but quadriceps endurance declined for the HP/MC group during the experimental week. In conclusion, a hypoenergy diet providing twice the RDA for protein was more effective in retaining body protein in WL than a diet with higher carbohydrate but the RDA for protein. However, the lower carbohydrate of this diet contributed to reduced muscular endurance in these athletes.

No abstract

This study reports the results of one effort to help supermarket shoppers alter food purchases to make purchases (and meals) that are lower in fat and higher in fiber. A prototype interactive information system using instructional video programs, feedback on purchases with specific goals for change, weekly programs, and the ability to track user interactions and intended purchases was evaluated. The major dependent measure was users' actual food purchases as derived from participants' highly detailed supermarket receipts. After a 5- to 7-week baseline phase, participants were randomly assigned to an experimental or control condition for the 7- to 8-week intervention phase. A follow-up phase began 5 to 8 weeks after participants completed the intervention and discontinued use of the system. The results indicated that experimental participants, when compared to control participants, decreased high fat purchases and increased high fiber purchases during intervention, with evidence for some maintenance of effect in follow-up. Plans for increasing the use and impact of the system are discussed.

Weight reduction is a goal common to obese persons and some athletic groups. An optimal weight loss programme for both populations should selectively deplete body fat while maintaining lean tissue. Another concern, particularly for athletes but also for obese persons participating in an exercise programme, is maintenance of physical performance. Treatments relying only on energy restriction commonly cause substantial loss of lean tissue, but the addition of aerobic exercise has frequently been shown to reduce this loss. Although less commonly used, resistance exercise appears to prevent loss of or even increase muscle mass during energy restriction. This type of exercise is less likely than aerobic exercise to acutely increase energy and lipid utilisation but may increase lean tissue, metabolic rate and thus indirectly aid weight reduction. Impairment of aerobic capacity, aerobic endurance, and muscle dysfunction has been demonstrated during energy restriction in athletes and obese persons. Incorporation of exercise into the weight loss programme may alleviate some of these negative consequences on performance. The addition of aerobic exercise of adequate intensity and duration has been shown to improve aerobic performance, even during severe energy restriction in obese individuals. Although resistance exercise will not cause an improvement of aerobic performance, increase in muscle size and strength have been noted concurrent with substantial weight loss. In summary, the value of aerobic exercise during weight loss is clear but the place of resistance exercise is intriguing but unresolved. To make development of ideal treatments for weight loss even more complex, the quantity of protein and carbohydrate in the energy-restricted diets may interact with the exercise prescription to determine the influence of the programme on body composition and physical performance in athletes and obese individuals.

No abstract