American Diabetes Association's 73rd Scientific Sessions:

Fat, Protein Raise Blood Glucose in Children With Type 1 Diabetes


Current practice in calculating insulin dosing relies mainly on carbohydrate counting, with less emphasis on the impact of protein and fat on blood glucose. But new research suggests that protein and fat each affect blood glucose long after a meal, and that their combined effect is greater than the sum of their parts.

The study involved 33 children and adolescents between ages 7 and 18 with type 1 diabetes. Their diabetes was well controlled through use of an insulin pump or multiple daily injections, and participants had an average A1c of 7.2%, noted study researcher Carmel E. Smart, APD, PhD, a Specialist Diabetes Dietitian at the John Hunter Children’s Hospital and Hunter Medical Research Institute, in Newcastle, New South Wales.

Participants in the Australian study were given test breakfasts on four consecutive days. All breakfasts had 30 g of carbohydrates, but varying amounts of protein and fat. Additional protein came from powdered supplements and additional fat came from double cream (heavy cream) as part of the breakfast. The low-protein, low-fat (LP/LF), or control breakfast contained 5 g of protein and 4 g of fat; the high-protein, low-fat (HP/LF) breakfast contained 40 g of protein and 4 g of fat; the low-protein, high-fat (LP/HF) breakfast contained 5 g of protein and 35 g of fat; and the high-protein, high-fat (HP/HF) breakfast contained 40 g of protein and 35 g of fat. Participants received their usual individually standardized insulin dose for each breakfast.

All participants wore a continuous glucose monitoring system, and the researchers recorded the participants’ postprandial blood glucose every 30 minutes for 5 hours after the meal. Study participants did not receive snacks or engage in physical activity for the 5 hours of glucose monitoring.

Blood glucose levels tended to peak at roughly the 90-minute mark after all meals, but declined at different rates thereafter, most notably after 2.5 hours, reported the investigators. Compared with the LP/LF (control) breakfast, by the 5-hour mark the participants’ blood glucose was on average 45 mg/dL higher after the HP/LF breakfast, 63 mg/dL higher after the LP/HF breakfast, and 97.2 mg/dL higher after the HP/HF breakfast.

“The effect of protein and fat was additive at all time points after 150 minutes,” said Dr. Smart. “Protein and fat should be considered in prandial insulin dose and distribution.”

According to Melinda Maryniuk, MEd, RD, CDE, Director, Clinical and Education Programs at Joslin Diabetes Center in Boston, the findings appear to be in line with what patients and clinicians have seen anecdotally.

“Patients have long been reporting that certain meals containing more protein and fat keep them feeling full longer. Thus, one would expect glucose levels would stay elevated for a longer time after a breakfast of eggs, bacon, and toast compared to a breakfast equal in carbohydrates but low in protein and fat, such as toast and fruit,” said Ms. Maryniuk. “While there has not been much research to confirm this, many clinicians who work with this population recognize that fat and protein must play some role and have been advising patients to check post-meal blood glucose levels after meals that are higher in fat and protein to assess the glycemic impact. So, while the results are not surprising, it is important to have this documented in a more controlled setting.”

There were 29 hypoglycemic events in the study. Compared with the LF/LP breakfast, there were fewer events after high-protein breakfasts, but no reduction after high-fat breakfasts.

Dr. Smart speculated on the potential usefulness of eating protein later in the day. “Protein may have a protective effect on hypoglycemia. The evening might be the most important time to consider insulin dosing and protein because [children] will not test [their blood glucose] or have another meal or snack for a relatively long time.”

Ms. Maryniuk noted the study design and suggested the need for further research. “In the study, a pure protein powder was added. In reality, most protein-based foods commonly enjoyed such as nuts, cheese, lean meats, and fish, include some amount of fat. This deserves further study with a variety of protein foods to see if similar results are achieved,” she said. “Based on this work, it is certainly sage advice to include some low-fat protein as part of an evening snack to reduce the risk of nocturnal hypoglycemia, such as a lean meat sandwich, Greek yogurt, or a fruit and nut mix.”


Continuous blood-glucose monitors were provided by Medtronic.

Dr. Smart and Ms. Maryniuk disclosed no conflicts of interest. 

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