The Role of Phosphorus in Diet Induced Thermogenesis (DIT) of Both Lean and Obese Subjects

Subject will be advice to take a weight maintenance diet which contains at least 250-300g of carbohydrate per day for the 3 days before each study day and also he/she will be asked to avoid any intense physical activity during the day before the day of the test. Overnight fasted subjects (> 8 hours) will be requested to attend the testing room at around 8:00 am. The he investigators will take the anthropometric measurements (weight, height, waist circumference) and determine blood glucose.

A crossover design study will be used in which each subject will undertake 2 or 3 sessions in a random order over 2 or 3 different days which are separated by a minimum of one week. The difference between the sessions is the ingestion of placebo ( 4 tablets) or phosphorus (4 tablets, each contain 125mgof phosphorus) tablets with the appropriate meal.

Specific Aim 1: The impact of phosphorus ingestion on DIT of lean and obese subjects consuming high carbohydrate meal (Table 1: Meal 1).

This will be divided into two experiments:

Experiment 1.1: The impact of phosphorus ingestion on DIT of lean subjects consuming high carbohydrate meal (16 subjects).

In this experiment, overnight fasted lean subjects (> 8 hours) will be requested to attend the testing room at around 8:00 am. Anthropometric measurements (weight, height, waist circumference) will be taken, rest for 30 min, measure resting energy expenditure (REE) for 30 min, ingest meal with the appropriate supplement and measure postprandial energy expenditure (PEE) for 4 hours (see figure 3). In this experiment, subject will undertake 3 sessions in a random order over 3 different days which are separated by a minimum of one week.

Session 1: Ingestion of phosphorus tablets (4 tablets) alone. No meal. Needed to determine the impact of phosphorus alone on DIT Session 2: Ingestion of phosphorus tablets (4 tablets) with the high carbohydrate meal (table1: Meal 1).

Session 3: Ingestion of placebo tablets (4 tablets) with the high carbohydrate meal (table 1: Meal 1).

Experiment 1.2: The impact of phosphorus ingestion on DIT of lean subjects consuming high carbohydrate meal (16 subjects).

In this experiment, overnight fasted obese subjects (> 8 hours) will be requested to attend the testing room at around 8:00 am. Anthropometric measurements (weight, height, waist circumference) will be taken, rest for 30 min, measure resting REE for 30 min, ingest meal with the appropriate supplement and measure PEE for 4 hours (see figure 3). In this experiment, subject will undertake 3 sessions in a random order over 3 different days which are separated by a minimum of one week.

Session 1: Ingestion of phosphorus tablets (4 tables) alone. No meal. Needed to determine the impact of phosphorus alone on DIT Session 2: Ingestion of phosphorus tablets (4 tables) with the high carbohydrate meal (Table 1:Meal 1).

Session 3: Ingestion of placebo tablets (4 tables) with the high carbohydrate meal (Table 1:Meal 1).

Specific Aim 2: The impact of phosphorus ingestion on DIT of lean and obese subjects consuming high protein-low phosphorus meal (table 1: Meal 2).

This will be divided into two experiments:

Experiment 2.1: The impact of phosphorus ingestion on DIT of lean and obese subjects consuming high protein-low phosphorus meal (16 subjects).

In this experiment, overnight fasted lean subjects (> 8 hours) will be requested to attend the testing room at around 8:00 am. Anthropometric measurements (weight, height, waist circumference) will be taken, rest for 30 min, measure REE for 30 min, ingest meal with the appropriate supplement and measure PEE for 4 hours (see figure 3). In this experiment, subject will undertake 2 sessions in a random order over 2 different days which are separated by a minimum of one week.

Session 1: Ingestion of phosphorus tablets (4 tablets) with the high protein meal (table1: Meal 2).

Session 2: Ingestion of placebo tablets (4 tablets) with the high protein meal (table 1: Meal 2).

Experiment 2.2: The impact of phosphorus ingestion on DIT of lean and obese subjects consuming high protein-low phosphorus meal (16 subjects).

In this experiment, overnight fasted obese subjects (> 8 hours) will be requested to attend the testing room at around 8:00 am. Anthropometric measurements (weight, height, waist circumference) will be taken, rest for 30 min, measure REE for 30 min, ingest meal with the appropriate supplement and measure PEE for 4 hours (see figure 3). Urine sample over the experimental period will be collected. In this experiment, subject will undertake 2 sessions in a random order over 2 different days which are separated by a minimum of one week.

Session 1: Ingestion of phosphorus tablets (4 tablets) with the high protein meal (table1: Meal 2).

Session 2: Ingestion of placebo tablets (4 tablets) with the high protein meal (table 1: Meal 2).

Inclusion criteria

• lean subjects (BMI between 20 and 25);
• obese (BMI above 30) subjects

Exclusion criteria

• Pregnant and lactating women
• Subjects on regular use of medication that affects body weight
• weight loss of 3% or more in the preceding 3 months
• Subjects with kidney disease