T2 Diabetes and Low-Calorie Diets

Precautions and Disclaimer:  See page bottom.

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This document addresses issues involved when someone with type 2 diabetes starts a reduced-calorie balanced diet to lose excess fat weight.  Low-carbohydrate and very low-carb diets diets are addressed elsewhere. 

Weight loss is one of the most powerful treatments for overweight people with type 2 diabetes mellitus.  Insulin shots and other medications never cure the illness; they help control it.  Some overweight diabetics can actually cure their condition with sufficient loss of excess fat.  But weight loss is slow.  Two of the most potent tools for quickly reducing elevated blood sugar levels are 1) restriction of calorie intake, and 2) exercise.

Diabetes mellitus occurs in two forms, oddly enough called type 1 and type 2.  Typically diagnosed in childhood, type 1 diabetes is also known as juvenile-onset or insulin-dependent.  Insulin is a natural hormone that 1) lowers blood glucose (sugar) levels by driving it into cells for immediate use or storage as glycogen, 2) stimulates formation of proteins, and 3) promotes fat tissue accumulation.  Type 1 diabetics lack insulin, are not usually overweight, and do not live long without insulin shots.  My comments hereafter are directed toward the more common diabetes, type 2.

Most diabetics are type 2, also referred to as adult-onset or non-insulin-dependent.  Although sometimes treated with insulin shots, these diabetics do not die soon if the shots are stopped, and many do quite well without insulin injections.  So their lives are not “dependent” on insulin injections, in contrast to the type 1 diabetics.  Eighty-five percent of type 2 diabetics are overweight.  In addition to excessive body fat, genetic factors and aging contribute to the incidence of type 2 diabetes.  These diabetics have plenty of insulin, often more than average, but the body is resistant to insulin’s effect.  In order to overcome this resistance, the body produces more insulin, which may contribute to the hypertension, lipid abnormalities, and vascular problems so often seen in diabetics.

The primary treatment for overweight type 2 diabetics is reduction of excess body fat.  Admittedly, many diabetics have great difficulty with weight management.  I have often felt that it must be harder for them than for non-diabetics, perhaps related to diabetic physiology or genetics.  Even if all the excess weight can’t be lost, significant metabolic improvements are seen with loss of just 10 to 20 pounds (4.5 -9 kg). 

If you are a diabetic trying to get and stay healthy, you need at least two other players on your healthcare team: a registered dietitian and a personal physician.  Additionally, diabetes nurse educators can be quite helpful in teaching you to manage your condition.  Dietitians are particularly helpful consultants when diabetes is first diagnosed and periodically thereafter to answer food questions, check on compliance with diet recommendations, and to review new dietary guidelines.  Most primary care physicians such as family physicians and internists are well-trained to co-manage diabetes with you.  Endocrinologists can also be very helpful.

I will assume hereafter that you are an overweight type 2 diabetic planning on starting a balanced, reduced-calorie diet, eating 300 to 500 calories per day less than your usual habit.  How do you know your current daily calorie intake?  You could eat your usual foods for one week, recording everything you ate and how many calories it contained, then divide the total calories by seven.  Alternatively, you could consult an online “daily needs calculator” and get a rough estimate.  Many women – overweight or not –  normally eat 1,800 to 2,200 calories daily. 

Your glucoses may already be under good control.  On the other hand, perhaps they run 200–400 mg/dl all the time.  Your diabetes may be treated thus far only with a “diabetic diet.”  More likely, you are one of millions treated with diet and medications:

• Metformin
• Sulfonylureas: glipizide, glyburide, glimiperide, chlorpropamide, acetohexamide, tolbutamide
• Thiazoladinediones: pioglitazone, rosiglitazone
• Insulin
• Meglitinides: repaglinide, nateglinide
• Alpha-glucosidase inhibitors: acarbose, miglitol
• Pramlintide
• Exenatide
• DPP-4 inhibitors: sitagliptan, saxagliptin
• Bile acid sequestrant: colesevelam
• Dopamine agonist: bromocriptine
• Other agents

The first four drug classes listed are by far the most commonly used ones.  I utilize generic names here.  Your pill bottle may feature the brand or trade name of these products but should also list the generic name.  Be sure which class you are taking.

First off, get your personal physician’s and dietitian’s blessings to start a reduced- calorie diet.

Note that since 1994 the ADA has not endorsed any particular diet or specified percentages of carbohydrates, proteins, and fats.  There is no “ADA diet.”

The Amerian Diabetes Association in 2008 gave the go-ahead for use of low-carb diets as a weight-control method for type 2 diabetics.  Previously, the organization had recommended against diets that restrict carbohydrates to less than 130 grams daily.  (A baked potatoe without the skin has 30 grams.)  Understand that the ADA does not endorse low-carb diets for weight loss or diabetes management.  They simply say that either low-carb or low-fat calorie-restricted diets might be effective for up to one year. 

The most important things for your doctor and dietitian to know are that you will be eating less – 300 to 500 calories fewer per day – and whether you plan on exercising more.  Your doctor may well need to reduce the dose of your diabetic medication.

 Intake of carbohydrates is a key determinant of blood sugar levels in diabetics.  Both the amount of carbohydrate and type of carbohydrate are important.  The main sources of carbohydrates are:

• Grains
• Fruits
• Starchy vegetables (e.g., corn, white potatoes, peas, beans, sweet potatoes)
• Milk products
• Candy
• Sweetened beverages
• Other added sugars (e.g., high fructose corn syrup)

Since carbohydrates have so much influence on your blood glucose level, it is important for you to have consistent carbohydrate intake throughout the day.  Distribute your carbohydrate intake evenly throughout the day, as with each of three meals and perhaps also as a late evening snack.  Otherwise you may swing wildly between glucoses too high and too low, whether you feel it or not.

Hypoglycemia 

Hypoglycemia is the biggest immediate risk for a diabetic starting a calorie-restricted diet, with or without a new exercise program.  Hypoglycemia means an abnormally low blood sugar (under 60–70 mg/dl) associated with symptoms such as weakness, malaise, anxiety, irritability, shaking, sweating, hunger, fast heart rate, blurry vision, difficulty concentrating, or dizziness.  Symptoms often start suddenly and without obvious explanation.  If not recognized and treated, hypoglycemia can lead to incoordination, altered mental status (fuzzy thinking, disorientation, confusion, odd behavior, lethargy), loss of consciousness, seizures, and even death (rare). 

Your personal physician and other healthcare team members will teach you how to recognize and manage hypoglycemia.  Immediate early stage treatment involves ingestion of glucose or other carbohydrate: six fl oz (180 ml) sweetened fruit juice, 12 fl oz ( 360 ml) milk, four tsp (20 ml) table sugar mixed in water, four fl oz (120 ml) soda pop, candy, glucose tablets or paste, etc.  Fifteen to 30 grams of glucose or other carbohydrate should do the trick.  Hypoglycemic symptoms respond within 20 minutes.

If level of consciousness is diminished such that the person cannot safely swallow, he will need a glucagon injection.  Non-medical people can be trained to give the injection under the skin or into a muscle.  Ask your doctor if you are at risk for severe hypoglycemia.  If so, ask him for a prescription so you can get an emergency glucagon kit from a pharmacy. 

Do not assume your sugar is low every time you feel a little hungry, weak, or anxious.  Use your home glucose monitor for confirmation when able.  If you do experience hypoglycemia, discuss management options with your doctor: medication adjustment, eating more calories per day, shifting meal quantities or times, adjustment of exercise routine, etc.  Eating at regular intervals three or four times daily helps prevent hypoglycemia. 

Diabetics not being treated with pills or insulin rarely need to worry about hypoglycemia.  Similarly, diabetics treated only with diet, metformin, colesevalam, and/or an alpha-glucosidase inhibitor should not have much, if any, trouble with hypoglycemia.  Sitagliptan and saxagliptin do not seem to cause low glucose levels, whether used alone or combined with metformin or a thiazoladinedione.  Thiazolidinediones by themselves cause hypoglycemia in only 1 to 3% of users; perhaps a higher percentage in people on a reduced calorie diet.  As of August 30, 2009, I’m not sure if bromocriptine by itself causes hypoglycemia: I suspect not, but check with your own doctor or pharmacist.

Hypoglycemia is a concern, however, for diabetics taking certain other medications: insulin, sulfonylureas, thiazolidinediones, meglitinides, pramlintide plus insulin, exenatide plus sulfonylurea.  If you are treated with any of these, you may or may not require a downward adjustment in dosage.  It depends on what your glucoses are running before you start your diet.  For example, if your pre-diet fasting glucoses are always over 200 mg/dl and post-prandial (after meal) glucoses are consistently over 250, you probably don’t need any downward adjustment of drug dosages when you start the diet.  Your glucoses have room to fall safely.  Nevertheless, you should monitor your sugars on your home glucose monitor frequently during the first week of the diet: before each meal and at bedtime, more often if you sense your glucose is too high or low. 

On the other hand, your glucoses may be under good control prior to initiation of the diet: fasting glucoses 90 to 130 mg/dl, after-meal glucoses under 180.  In this circumstance, your doctor should suggest reducing your medication dose by about 25 percent, or stopping one of your diabetic medications if you take more than one.  Of course, monitor your sugars by machine before meals and at bedtime during the first week of your diet, at least.  Monitor more often if you suspect hypoglycemia or worry about it. 

A reduced-calorie diet will quite often lower your glucose levels, perhaps dangerously low if you don’t reduce drug dosages appropriately.

Exercise and Blood Glucose Levels

Remember that exercising muscles soak up bloodstream glucose as an energy source, leaving less circulating glucose available for other tissues such as your brain.  Vigorous exercise can reduce blood sugar levels below 60, although it is rarely a problem in non-diabetics.  The degree of glucose removal from the bloodstream depends on how much muscle is working, and how hard.  Vigorous exercise by several large muscles will remove more glucose.  Of course, other metabolic processes are working to put more glucose into circulation as exercising muscles remove it.  Carbohydrate intake and diabetic medications are going to affect this balance one way or the other. 

Many reduced-calorie diet programs recommend exercising at least lightly, such as brisk walking 30 minutes daily.  If your diabetic medication is insulin, a sulfonylurea, a meglitinide, pramlintide plus insulin, or exetanide plus sulfonylurea, you should check your blood sugar level just before you exercise.  If under 100 mg/dl, eat some carbohydrate – perhaps 100-150 calories – before exercising.  Or hold off on exercise until later, perhaps after a meal when your glucose level will be over 100. 

Carbohydrate supplementation before or during exercise is not usually necessary if you are treated only with diet, a thiazoladinedione, metformin, an alpha-glucosidase inhibitor, and/or sitagliptan phosphate.  Nonetheless, keep a carbohydrate source with you or nearby in case you develop hypoglycemia during exercise. 

These general guidelines do not apply across the board to each and every diabetic.  Our metabolisms are all different.  The best way to see what effect diet and exercise will have on your glucose levels is to monitor them with your home glucose device, especially if you are new to exercise or you work out vigorously.  You can pause during your exercise routine and check a glucose level, particularly if you don’t feel well.  Calorie restriction plus a moderately strenuous or vigorous exercise program may necessitate a 50 percent or more reduction in drug dosages.  Or the dosage may need to be reduced only on days of heavy workouts.  Again, enlist the help of your personal physician, dietitian, diabetes nurse educator, and home glucose monitor. 

After you lose a significant amount of weight, such as 10 percent of your pre-diet weight, you can plan on needing less glucose-lowering drugs.  So as you improve your health, you also save money on your drug bill.  With enough weight loss, you may even cure your diabetes.

Steve Parker, M.D.

Precautions and Disclaimer:  The ideas and suggestions in this document are provided as general educational information only and should not be construed as medical advice or care.  Information herein is meant to complement, not replace, any advice or information from your personal health professional.  All matters reagarding your health require supervision by a personal physician or other appropriate health professional familiar with your current health status.  Always consult your personal physician before making any dietary or exercise changes.  Steve Parker, M.D., pxHealth, and Vanguard Press disclaim any liability or warranties of any kind arising directly or indirectly from use of this document.  If any problems develop, always consult your personal physician.  Only your physician can provide you medical advice.

Last updated August 30, 2009