Insulin Resistance and Pre-Diabetes
Insulin resistance is a silent condition that increases the chances
of developing diabetes and heart disease. Learning about insulin
resistance is the first step you can take toward making lifestyle
changes that will help you prevent diabetes and other health problems.
What does insulin do?
After you eat, the food is broken down into glucose, the simple
sugar that is the main source of energy for the body's cells. But
your cells cannot use glucose without insulin, a hormone produced
by the pancreas. Insulin helps the cells take in glucose and convert
it to energy. When the pancreas does not make enough insulin or
the body is unable to use the insulin that is present, the cells
cannot use glucose. Excess glucose builds up in the bloodstream,
setting the stage for diabetes.
Being obese or overweight affects the way insulin works in your
body. Extra fat tissue can make your body resistant to the action
of insulin, but exercise helps insulin work well.
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How are insulin resistance, pre-diabetes, and type 2 diabetes linked?
If you have insulin resistance, your muscle, fat, and liver cells
do not use insulin properly. The pancreas tries to keep up with
the demand for insulin by producing more. Eventually, the pancreas
cannot keep up with the body's need for insulin, and excess glucose
builds up in the bloodstream. Many people with insulin resistance
have high levels of blood glucose and high levels of insulin circulating
in their blood at the same time.
People with blood glucose levels that are higher than normal but
not yet in the diabetic range have "pre-diabetes." Doctors sometimes
call this condition impaired fasting glucose (IFG) or impaired glucose
tolerance (IGT), depending on the test used to diagnose it. In a cross-section of U.S. adults aged 40 to 74 tested during the period 1988 to 1994, 33.8 percent had IFG, 15.4 percent had IGT, and 40.1 percent had pre-diabetes (IGT or IFG or both). Applying these percentages to the 2000 U.S. population, about 35 million adults aged 40 to 74 would have IFG, 16 million would have IGT, and 41 million would have pre-diabetes.
If you have pre-diabetes, you have a higher risk of developing
type 2 diabetes, formerly called adult-onset diabetes or noninsulin-dependent
diabetes. Studies have shown that most people with pre-diabetes
go on to develop type 2 diabetes within 10 years, unless they lose
5 to 7 percent of their body weight--which is about 10 to 15 pounds
for someone who weighs 200 pounds--by making modest changes in their
diet and level of physical activity. People with pre-diabetes also
have a higher risk of heart disease.
Type 2 diabetes is sometimes defined as the form of diabetes that
develops when the body does not respond properly to insulin, as
opposed to type 1 diabetes, in which the pancreas makes no insulin
at all. At first, the pancreas keeps up with the added demand by
producing more insulin. In time, however, it loses the ability to
secrete enough insulin in response to meals.
Insulin resistance can also occur in people who have type 1 diabetes,
especially if they are overweight.
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What causes insulin resistance?
Because insulin resistance tends to run in families, we know that
genes are partly responsible. Excess weight also contributes to
insulin resistance because too much fat interferes with muscles'
ability to use insulin. Lack of exercise further reduces muscles'
ability to use insulin.
Many people with insulin resistance and high blood glucose have
excess weight around the waist, high LDL (bad) blood cholesterol
levels, low HDL (good) cholesterol levels, high levels of triglycerides
(another fat in the blood), and high blood pressure, all conditions
that also put the heart at risk. This combination of problems is
referred to as the metabolic syndrome, or the insulin resistance
syndrome (formerly called Syndrome X).
Metabolic Syndrome
Metabolic syndrome is defined by the National Cholesterol Education Program as the presence of any three of the following conditions:
- excess weight around the waist (waist measurement of more
than 40 inches for men and more than 35 inches for women)
- high levels of triglycerides (150 mg/dL or higher)
- low levels of HDL, or "good," cholesterol (below 40 mg/dL for men and below 50 mg/dL for women)
- high blood pressure (130/85 mm Hg or higher)
- high fasting blood glucose levels (110 mg/dL or higher)
Source: National Cholesterol Education
Program, Third Report of the Expert Panel on Detection, Evaluation,
and Treatment of High Blood Cholesterol in Adults (Adult Treatment
Panel III), National Heart, Lung, and Blood Institute, National
Institutes of Health, May 2001.
Note: Other definitions of similar conditions have been developed by the World Health Organization and the Association of Clinical Endocrinologists.
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What are the symptoms of insulin resistance and pre-diabetes?
Insulin resistance and pre-diabetes usually have no symptoms. You
may have one or both conditions for several years without noticing
anything. If you have a severe form of insulin resistance, you may
get dark patches of skin, usually on the back of your neck. Sometimes
people get a dark ring around their neck. Other possible sites for
these dark patches include elbows, knees, knuckles, and armpits.
This condition is called acanthosis nigricans.
If you have a mild or moderate form of insulin resistance, blood
tests may show normal or high blood glucose and high levels of insulin
at the same time.
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Do you have insulin resistance or pre-diabetes?
Anyone 45 years or older should consider getting tested for diabetes. If you are overweight and aged 45 or older, it is strongly recommended that you get tested. You should consider getting tested if you are younger than
45, overweight, and have one or more of the following risk factors:
- family history of diabetes
- low HDL cholesterol and high triglycerides
- high blood pressure
- history of gestational diabetes (diabetes during pregnancy)
or gave birth to a baby weighing more than 9 pounds
- minority group background (African American, American Indian,
Hispanic American/Latino, or Asian American/Pacific Islander)
Diabetes and pre-diabetes can be detected with one of the following
tests:
A fasting glucose test measures your blood glucose after
you have gone overnight without eating. This test is most reliable
when done in the morning. Fasting glucose levels of 100 to 125 mg/dL
are above normal but not high enough to be called diabetes. This
condition is called pre-diabetes or impaired fasting glucose,
and it suggests that you have probably had insulin resistance for
some time. IFG is considered a pre-diabetic state, meaning that
you are more likely to develop diabetes but do not have it yet.
A glucose tolerance test measures your blood glucose after
an overnight fast and 2 hours after you drink a sweet liquid provided
by the doctor or laboratory. If your blood glucose falls between
140 and 199 mg/dL 2 hours after drinking the liquid, your glucose
tolerance is above normal but not high enough for diabetes. This
condition, also a form of pre-diabetes, is called impaired glucose
tolerance and, like IFG, it points toward a history of insulin
resistance and a risk for developing diabetes.
These tests give only indirect evidence of insulin resistance.
The test that most accurately measures insulin resistance is too
complicated and expensive to use as a screening tool in most doctors'
offices. The test, called the euglycemic clamp, is a research tool
that helps scientists learn more about sugar metabolism problems.
Insulin resistance can also be assessed with measurement of fasting
insulin. If conventional tests show that you have IFG or IGT, your
doctor may suggest changes in diet and exercise to reduce your risk
of developing diabetes.
If your blood glucose is higher than normal but lower than the diabetes range, have your blood glucose checked in 1 to 2 years.
Lab Tests and What They Show
- Blood glucose. High blood glucose may be a sign that
your body does not have enough insulin or does not use it well.
However, a fasting measurement or oral glucose tolerance test
gives more precise information.
- Insulin. An insulin measurement helps determine whether
a high blood glucose reading is the result of insufficient insulin
or poor use of insulin.
- Fasting glucose. Your blood glucose level should be
lower after several hours without eating. After an overnight fast,
the normal level is below 100 mg/dL. If it is in the 100 to 125
mg/dL range, you have impaired fasting glucose or pre-diabetes.
A result of 126 or higher, if confirmed on a repeat test, indicates
diabetes.
- Glucose tolerance. Your blood glucose level will be
higher after drinking a sugar solution, but it should still be
below 140 mg/dL 2 hours after the drink. If it is higher than
normal (in the 140 to 199 mg/dL range) 2 hours after drinking
the solution, you have IGT or pre-diabetes, which is another strong
indication that your body has trouble using glucose. A level of
200 or higher, if confirmed, means diabetes is already present.
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Can you reverse insulin resistance?
Yes. Physical activity and weight loss make the body respond better
to insulin. By losing weight and being more physically active, you
may avoid developing type 2 diabetes. In fact, a major study has
verified the benefits of healthy lifestyle changes and weight loss.
In 2001, the National Institutes of Health completed the Diabetes
Prevention Program (DPP), a clinical trial designed to find the
most effective ways of preventing type 2 diabetes in overweight
people with pre-diabetes. The researchers found that lifestyle changes
reduced the risk of diabetes by 58 percent. Also, many people with
pre-diabetes returned to normal blood glucose levels.
The main goal in treating insulin resistance and pre-diabetes is
to help your body relearn to use insulin normally. You can do several
things to help reach this goal.
Be Active and Eat Well
Physical activity helps your muscle cells use blood glucose because
they need it for energy. Exercise makes those cells more sensitive
to insulin.
The DPP confirmed that people who follow a low-fat, low-calorie
diet and who increase activities such as walking briskly or riding
a bike for 30 minutes, five times a week, have a far smaller risk
of developing diabetes than people who do not exercise regularly.
The DPP also reinforced the importance of a low-calorie, low-fat
diet. Following a low-calorie, low-fat diet can provide two benefits.
If you are overweight, one benefit is that limiting your calorie
and fat intake can help you lose weight. DPP participants who lost
weight were far less likely to develop diabetes than others in the
study who remained at an unhealthy weight. Increasing your activity
and following a low-calorie, low-fat diet can also improve your
blood pressure and cholesterol levels and has many other health
benefits.
Scientists have established some numbers to help people set goals
that will reduce their risk of developing glucose metabolism problems.
- Weight. Body mass index (BMI) is a measure used to evaluate
body weight relative to height. You can use BMI to find out whether
you are underweight, normal weight, overweight, or obese. Use
the Body Mass Index Table to find your BMI.
- Find your height in the left-hand column.
- Move across in the same row to the number closest to your weight.
- The number at the top of that column is your BMI. Check the
word above your BMI to see whether you are normal weight, overweight,
or obese. If you are overweight or obese, talk with your doctor
about ways to lose weight to reduce your risk of diabetes.
Body Mass Index Table
For a printer-friendly version of
this table, use the pdf.*
|
Normal |
Overweight |
Obese |
BMI |
19 |
20 |
21 |
22 |
23 |
24 |
25 |
26 |
27 |
28 |
29 |
30 |
31 |
32 |
33 |
34 |
35 |
36 |
Height
(inches) |
Body Weight
(pounds) |
58 |
91 |
96 |
100 |
105 |
110 |
115 |
119 |
124 |
129 |
134 |
138 |
143 |
148 |
153 |
158 |
162 |
167 |
172 |
59 |
94 |
99 |
104 |
109 |
114 |
119 |
124 |
128 |
133 |
138 |
143 |
148 |
153 |
158 |
163 |
168 |
173 |
178 |
60 |
97 |
102 |
107 |
112 |
118 |
123 |
128 |
133 |
138 |
143 |
148 |
153 |
158 |
163 |
168 |
174 |
179 |
184 |
61 |
100 |
106 |
111 |
116 |
122 |
127 |
132 |
137 |
143 |
148 |
153 |
158 |
164 |
169 |
174 |
180 |
185 |
190 |
62 |
104 |
109 |
115 |
120 |
126 |
131 |
136 |
142 |
147 |
153 |
158 |
164 |
169 |
175 |
180 |
186 |
191 |
196 |
63 |
107 |
113 |
118 |
124 |
130 |
135 |
141 |
146 |
152 |
158 |
163 |
169 |
175 |
180 |
186 |
191 |
197 |
203 |
64 |
110 |
116 |
122 |
128 |
134 |
140 |
145 |
151 |
157 |
163 |
169 |
174 |
180 |
186 |
192 |
197 |
204 |
209 |
65 |
114 |
120 |
126 |
132 |
138 |
144 |
150 |
156 |
162 |
168 |
174 |
180 |
186 |
192 |
198 |
204 |
210 |
216 |
66 |
118 |
124 |
130 |
136 |
142 |
148 |
155 |
161 |
167 |
173 |
179 |
186 |
192 |
198 |
204 |
210 |
216 |
223 |
67 |
121 |
127 |
134 |
140 |
146 |
153 |
159 |
166 |
172 |
178 |
185 |
191 |
198 |
204 |
211 |
217 |
223 |
230 |
68 |
125 |
131 |
138 |
144 |
151 |
158 |
164 |
171 |
177 |
184 |
190 |
197 |
203 |
210 |
216 |
223 |
230 |
236 |
69 |
128 |
135 |
142 |
149 |
155 |
162 |
169 |
176 |
182 |
189 |
196 |
203 |
209 |
216 |
223 |
230 |
236 |
243 |
70 |
132 |
139 |
146 |
153 |
160 |
167 |
174 |
181 |
188 |
195 |
202 |
209 |
216 |
222 |
229 |
236 |
243 |
250 |
71 |
136 |
143 |
150 |
157 |
165 |
172 |
179 |
186 |
193 |
200 |
208 |
215 |
222 |
229 |
236 |
243 |
250 |
257 |
72 |
140 |
147 |
154 |
162 |
169 |
177 |
184 |
191 |
199 |
206 |
213 |
221 |
228 |
235 |
242 |
250 |
258 |
265 |
73 |
144 |
151 |
159 |
166 |
174 |
182 |
189 |
197 |
204 |
212 |
219 |
227 |
235 |
242 |
250 |
257 |
265 |
272 |
74 |
148 |
155 |
163 |
171 |
179 |
186 |
194 |
202 |
210 |
218 |
225 |
233 |
241 |
249 |
256 |
264 |
272 |
280 |
75 |
152 |
160 |
168 |
176 |
184 |
192 |
200 |
208 |
216 |
224 |
232 |
240 |
248 |
256 |
264 |
272 |
279 |
287 |
76 |
156 |
164 |
172 |
180 |
189 |
197 |
205 |
213 |
221 |
230 |
238 |
246 |
254 |
263 |
271 |
279 |
287 |
295 |
|
Obese |
Extreme Obesity |
BMI |
37 |
38 |
39 |
40 |
41 |
42 |
43 |
44 |
45 |
46 |
47 |
48 |
49 |
50 |
51 |
52 |
53 |
54 |
Height
(inches) |
Body Weight
(pounds) |
58 |
177 |
181 |
186 |
191 |
196 |
201 |
205 |
210 |
215 |
220 |
224 |
229 |
234 |
239 |
244 |
248 |
253 |
258 |
59 |
183 |
188 |
193 |
198 |
203 |
208 |
212 |
217 |
222 |
227 |
232 |
237 |
242 |
247 |
252 |
257 |
262 |
267 |
60 |
189 |
194 |
199 |
204 |
209 |
215 |
220 |
225 |
230 |
235 |
240 |
245 |
250 |
255 |
261 |
266 |
271 |
276 |
61 |
195 |
201 |
206 |
211 |
217 |
222 |
227 |
232 |
238 |
243 |
248 |
254 |
259 |
264 |
269 |
275 |
280 |
285 |
62 |
202 |
207 |
213 |
218 |
224 |
229 |
235 |
240 |
246 |
251 |
256 |
262 |
267 |
273 |
278 |
284 |
289 |
295 |
63 |
208 |
214 |
220 |
225 |
231 |
237 |
242 |
248 |
254 |
259 |
265 |
270 |
278 |
282 |
287 |
293 |
299 |
304 |
64 |
215 |
221 |
227 |
232 |
238 |
244 |
250 |
256 |
262 |
267 |
273 |
279 |
285 |
291 |
296 |
302 |
308 |
314 |
65 |
222 |
228 |
234 |
240 |
246 |
252 |
258 |
264 |
270 |
276 |
282 |
288 |
294 |
300 |
306 |
312 |
318 |
324 |
66 |
229 |
235 |
241 |
247 |
253 |
260 |
266 |
272 |
278 |
284 |
291 |
297 |
303 |
309 |
315 |
322 |
328 |
334 |
67 |
236 |
242 |
249 |
255 |
261 |
268 |
274 |
280 |
287 |
293 |
299 |
306 |
312 |
319 |
325 |
331 |
338 |
344 |
68 |
243 |
249 |
256 |
262 |
269 |
276 |
282 |
289 |
295 |
302 |
308 |
315 |
322 |
328 |
335 |
341 |
348 |
354 |
69 |
250 |
257 |
263 |
270 |
277 |
284 |
291 |
297 |
304 |
311 |
318 |
324 |
331 |
338 |
345 |
351 |
358 |
365 |
70 |
257 |
264 |
271 |
278 |
285 |
292 |
299 |
306 |
313 |
320 |
327 |
334 |
341 |
348 |
355 |
362 |
369 |
376 |
71 |
265 |
272 |
279 |
286 |
293 |
301 |
308 |
315 |
322 |
329 |
338 |
343 |
351 |
358 |
365 |
372 |
379 |
386 |
72 |
272 |
279 |
287 |
294 |
302 |
309 |
316 |
324 |
331 |
338 |
346 |
353 |
361 |
368 |
375 |
383 |
390 |
397 |
73 |
280 |
288 |
295 |
302 |
310 |
318 |
325 |
333 |
340 |
348 |
355 |
363 |
371 |
378 |
386 |
393 |
401 |
408 |
74 |
287 |
295 |
303 |
311 |
319 |
326 |
334 |
342 |
350 |
358 |
365 |
373 |
381 |
389 |
396 |
404 |
412 |
420 |
75 |
295 |
303 |
311 |
319 |
327 |
335 |
343 |
351 |
359 |
367 |
375 |
383 |
391 |
399 |
407 |
415 |
423 |
431 |
76 |
304 |
312 |
320 |
328 |
336 |
344 |
353 |
361 |
369 |
377 |
385 |
394 |
402 |
410 |
418 |
426 |
435 |
443 |
Source: Adapted from Clinical Guidelines
on the Identification, Evaluation, and Treatment of Overweight and
Obesity in Adults: The Evidence Report.
* pdf versions require the free
Adobe® Acrobat Reader software for viewing.
- Blood pressure. Blood pressure is expressed as two numbers
that represent pressure in your blood vessels when your heart
is beating (systolic pressure) and when it is resting (diastolic
pressure). The numbers are usually written with a slash--for example,
140/90, which is expressed as "140 over 90." For the general population,
blood pressure below 130/85 is considered normal, although people
whose blood pressure is slightly elevated and who have no additional
risk factors for heart disease may be advised to make lifestyle
changes--that is, diet and exercise--rather than take blood pressure
medicines. People who have diabetes, however, should take whatever
steps necessary, including lifestyle changes and medicine, to
reach a blood pressure goal of below 130/80.
- Cholesterol. Your cholesterol is usually reported with
three values: low density lipoprotein (LDL) cholesterol, high
density lipoprotein (HDL) cholesterol, and total cholesterol.
LDL cholesterol is sometimes called "bad" cholesterol, while HDL
cholesterol is called "good" cholesterol. To lower your risk of
cardiovascular problems if you have diabetes, you should try to
keep your LDL cholesterol below 100 and your total cholesterol
below 200.
If you have metabolic syndrome, your doctor may recommend weight
loss with diet and exercise, as well as medication to lower your
cholesterol and blood pressure levels.
Stop Smoking
In addition to increasing your risk of cancer and cardiovascular
disease, smoking contributes to insulin resistance. Quitting smoking
is not easy, but it could be the single smartest thing you can do
to improve your health. You will reduce your risk for respiratory
problems, lung cancer, and diabetes.
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Can medicines help?
Two classes of drugs can improve response to insulin and are used
by prescription for type 2 diabetes--biguanides and thiazolidinediones.
Other medicines used for diabetes act by other mechanisms. Alpha-glucosidase
inhibitors restrict or delay the absorption of carbohydrates after
eating, resulting in a slower rise of blood glucose levels. Sulfonylureas
and meglitinides increase insulin production.
The DPP showed that the diabetes drug metformin, a biguanide, reduced
the risk of diabetes in those with pre-diabetes but was much less
successful than losing weight and increasing activity. In another
study, treatment with troglitazone, a thiazolidinedione later withdrawn
from the market following reports of liver toxicity, delayed or
prevented type 2 diabetes in Hispanic women with a history of gestational
diabetes. Acarbose, an alpha-glucosidase inhibitor, has been effective
in delaying development of type 2 diabetes. Additional studies using
other diabetes medicines and some types of blood pressure medicines
to prevent diabetes are under way. No drug has been approved by
the Food and Drug Administration (FDA) specifically for insulin
resistance or pre-diabetes.
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Hope Through Research
Researchers sponsored by the National Institute of Diabetes and
Digestive and Kidney Diseases conducted the DPP to find the most
effective ways to prevent or delay the onset of type 2 diabetes.
Volunteers were recruited from groups known to be at particularly
high risk for IGT and type 2 diabetes. The study was designed to
compare the effectiveness of lifestyle changes (weight loss through
exercise and diet) with drug therapy (metformin). A control group
received a placebo and information on diet and exercise. Participants
assigned to the intensive lifestyle intervention reduced their risk
of getting type 2 diabetes by 58 percent over 3 years. Participants
treated with metformin reduced their risk by 31 percent. Metformin
is not currently approved for use in preventing diabetes, but the
FDA may determine whether to make diabetes prevention an added indication
for this drug. In any event, the DPP demonstrates that a healthy
diet and exercise are the most effective treatment for insulin resistance
and the prediabetic states of IFG and IGT.
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Points to Remember
- Glucose is the simple sugar that is the main source of energy
for the body's cells.
- Insulin helps cells take in blood glucose and convert it to
energy.
- If you have insulin resistance, your body's cells do not respond
well to insulin.
- Insulin resistance is a stepping-stone to type 2 diabetes.
- Lack of exercise and excess weight contribute to insulin resistance.
- Engaging in moderate physical activity and maintaining proper
weight can help prevent insulin resistance.
- Insulin resistance plays a role in the development of cardiovascular
disease, which damages the heart and blood vessels.
- Controlling blood pressure and LDL cholesterol and not smoking
can also help prevent cardiovascular problems.
- The Diabetes Prevention Program confirmed that exercise and
a low-calorie, low-fat diet are the best ways to prevent type
2 diabetes.
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National Diabetes Information Clearinghouse
1 Information Way
Bethesda, MD 20892-3570
Email: ndic@info.niddk.nih.gov
The National Diabetes Information Clearinghouse (NDIC) is a service
of the National Institute of Diabetes and Digestive and Kidney Diseases
(NIDDK). The NIDDK is part of the National Institutes of Health
under the U.S. Department of Health and Human Services. Established
in 1978, the clearinghouse provides information about diabetes to
people with diabetes and to their families, health care professionals,
and the public. NDIC answers inquiries, develops and distributes
publications, and works closely with professional and patient organizations
and Government agencies to coordinate resources about diabetes.
Publications produced by the clearinghouse are carefully reviewed
by both NIDDK scientists and outside experts. This fact sheet was
reviewed by George A. Bray, M.D., Pennington Biomedical Research
Center, Louisiana State University; and Richard F. Hamman, M.D.,
Dr.P.H., Department of Preventive Medicine and Biometrics, University
of Colorado Health Sciences Center.
This e-text is not copyrighted. The clearinghouse encourages users
of this e-pub to duplicate and distribute as many copies as desired.
NIH Publication No. 04-4893
May 2004
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