Glycemic Response of Healthy Adults to GR2 Control™ Meal Replacement Protein Shake, SlimFast® And A Cereal/Juice-based Breakfast


February 28, 2001

Health Research and Studies Center (HRS), Los Altos, California
Gene A. Spiller, Ph.D., C.N.S.
Statistics by Stanley Morse, Ph.D.
Arianna Carughi, Ph.D., C.N.S., SAB Member, GNLD International


Purpose of the study was to compare the changes in serum glucose (glycemic response) induced by GNLD’s meal replacement protein shake to that induced by a popular, mass market diet drink (SlimFast®) and by a popular cereal/juice-based breakfast.

A total of 12 were enrolled subjects, plus one male who participated as a special subject. One female dropped out after the first test. Subjects had a screening serum glucose test performed at a local clinical laboratory to determine study eligibility. The protocol was reviewed and approved by the HRS independent review committee. Each subject signed an informed consent form and the Subjects’ Bill of Rights.


Inclusion Criteria

• female
• 35 to 60 years of age
• no known major health problems or disease
• normal overnight fasting blood sugar levels (less than 105 mg/dL and equal or greater than 70 mg/dL)

Subjects were asked to consume a standard dinner the night before each testing date and came to the Center having fasted for 12 hours. No food or alcohol was allowed after 8:00 p.m. the night before a test. Only water is allowed during the fast and the morning of a test (no coffee, tea, etc.) Subjects must refrain from strenuous exercise the day prior to testing.

Each subject was tested three times: one day per test meal, with a rest period of two weeks between each test day. On the first testing day, all subjects received the regular breakfast (see test meals below). On the second and third testing days, half of the subjects received the SlimFast, and the other half received GNLD’s meal replacement protein shake in a random sequence.

Subjects’ average age was 48±5 (mean±SD - 40 to 54 years)

Test Meals
• Regular breakfast consisting of 1 serving of cereal with 1% low-fat milk and 6 oz. orange juice
• SlimFast, vanilla flavor, one serving
• GNLD’s vanilla meal replacement protein shake, one serving

Serum glucose levels were measured at fasting, and then 20, 40, 60, 90 and 120 minutes after the meals were ingested. The test meals were to be consumed within 15 minutes.

Figure 1 ­ Comparison of serum glucose response for each treatment

as analyzed by Stanley Morse, Ph.D.

  FASTING 20 MIN 40 MIN 60 MIN 90 MIN 120 MIN
Cereal 84 131 112 91 79 74
GR2 Control 74 83 70 71 78 80
SlimFast 82 103 79 65 67 78

The three groups had similar glucose levels before eating breakfast. According to paired sample t-tests, glucose levels in the fasting condition did not differ from one another. There were however, major differences in glucose levels 20 and 40 minutes after eating breakfast. After both 20 and 40 minutes, glucose is higher in the Cereal condition than in the other two conditions. After 20 minutes, the GR2 Control and SlimFast conditions also differ from each other, with a lower level of glucose in the GR2 condition than in the SlimFast condition: t=4.50, df=11, p<.001. After 40 minutes, this GR2 vs. SlimFast difference disappears.

Although there is no difference among the three conditions after 60 minutes, after 90 minutes the GR2 vs. SlimFast difference re-emerges, but now the glucose level is higher in the GR2 condition than in the SlimFast condition: t=7.005, df=11, p<.001. After 90 minutes, the Cereal condition does not differ significantly from either of the other two conditions.