EVIDENCE-BASED CLINICAL PRACTICE

Dietary Calcium Intake and Obesity

Sarina Schrager, MD
Obesity is increasing in the United States in epidemic proportions. Epidemiologic data suggest that people with high calcium intake have a lower prevalence of overweight, obesity, and insulin resistance syndrome. Studies in transgenic mice have demonstrated that calcium influences adipocyte metabolism.
High calcium intake depresses levels of parathyroid hormone and 1,25-hydroxy vitamin D. These decreased hormone levels cause decreases in intracellular calcium, thereby inhibiting lipogenesis and
stimulating lipolysis. High dietary calcium intakes also increases excretion of fecal fat and may increase
core body temperature. Calcium from dairy products seems to have more of an impact than calcium
from dietary supplements. Primary care providers should include recommendations about adequate
calcium intake in standard dietary counseling about weight management. (J Am Board Fam Pract 2005;
18:205210.)

The prevalence of obesity is increasing dramatically

in the United States. Current data estimate that
more than 60% of the adult population between
the ages of 20 and 74 are obese or overweight.1 The
estimated annual direct and indirect costs of obesity
in the United States are close to $100 billion.2
Obesity prevalence has increased dramatically in
children as well.3,4 Overweight and obesity in children is directly associated with being overweight in
adulthood. Obesity is related to multiple disease
outcomes and has been shown to be related to
increased mortality rates. In fact, obesity will soon
overtake smoking as the most important modiable
cause of mortality in this country. Low calcium
intake has been identied as a potential contributing factor to obesity.5
Many diet studies have found the average dietary
calcium intake in people in the United States to be
much lower than the current recommendations.6
Dietary calcium is important in building bone mass
in children as well as in preventing osteoporosis in
the elderly. Only 30% of children in the United
States currently meet the recommended daily allowance (RDA) for calcium. The majority of dietary calcium consumed in the United States comes

Submitted, revised, 3 January 2005.

From the Department of Family Medicine, University of
WisconsinMadison. Address correspondence to Sarina
Schrager, MD, Department of Family Medicine, University
of WisconsinMadison, 777 S. Mills St., Madison, WI
53715 (e-mail: sbschrag@wisc.edu).

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from dairy products. The upper limit recommended for calcium is 2500 mg per day.
Low levels of dietary calcium and dairy products
increase the risk of hypertension and insulin resistance syndrome (IRS).79 The Coronary Artery
Risk Development in Young Adults (CARDIA)
study9 found that dairy product consumption was
inversely proportional to all components of the
IRS, including obesity. In this study, each daily
serving of a dairy product was associated with 21%
lower odds of developing IRS.
Epidemiologic studies have found an association
between dietary calcium intake and obesity. Animal
research has demonstrated a plausible physiologic
mechanism for such an association, and some human clinical trials have produced suggestive results.
The National Dairy Council has promoted the
association between eating dairy products and obesity prevention in a national advertising campaign
titled The Weight Is Over.
This article will review the epidemiologic data
supporting a relationship between dietary calcium
intake and obesity, explain the physiologic basis for
such a relationship, and present some supportive
recent data in humans. The article will conclude
with implications for primary care providers.

Epidemiologic Data Supporting the ObesityDietary Calcium Relationship

Several epidemiologic studies relate obesity prevalence and dietary calcium intake (Table 1). Zemel
et al10 reanalyzed National Health and Nutrition

Calcium Intake and Obesity

205

Table 1. Human Studies of Calcium and Weight

Author

Type of Study

Population

Results

Zemel et al10

Reanalysis of NHANES III data set

(SORT C)

380 women
7114 men

RR of being in the highest quartile for body

fat was reduced as calcium intake increased.
RR in second quartile of Ca2 intake was
0.75, in third RR quartile was 0.40, and in
highest quartile of Ca2 intake RR was 0.16
(P .0009 for women, P .0006 for men)

Davies et al13

Reanalysis of 5 clinical studies (2 crosssectional, 2 longitudinal, 1 RCT) of

calcium and bone density
(SORT C)

Total sample size among

all studies: 780 women
in 3rd, 5th, 8th
decades

Negative associations between calcium and

body weight found in all studies for all 3 age
groups. OR for being overweight (BMI
26) was 2.25 for young women who were
in the lower half of calcium intakes. In
RCT, calcium-treated women had
signicant weight loss over 4 years. Authors
estimate that a 1000-mg difference in
calcium intake may be responsible for an
8-kg difference in body weight.

Heaney et al11

Extension of reanalysis of above studies

(SORT C)

Young women (3rd

decade) n 348
Midlife women (5th
decade) n 216

Skinner et al14

Prospective cohort study examining

childrens body fat and calcium
intake from 2 months old to 8 years
old
(SORT B)
Prospective cohort study (Quebec
Family Study) measured twice
(between 1989 and 1994 and also
between 1995 and 2000)
(SORT B)
Cross-sectional study within a larger
prospective cohort study (the
HERITAGE Family Study)
(SORT B)

52 white child-mother
pairs completed entire
study (25 boys, 27
girls)

Young women: at 25% for calcium intake,

there was a 15% prevalence of overweight
and a 1.4% prevalence of obesity. At a
calcium intake equal to the current RDA,
the prevalence of overweight was only 4%
and obesity 0.2%. In midlife women, there
was a signicant decrease in yearly weight
gain with increasing calcium intakes.
Dietary calcium was negatively related to body
fat percentage in both boys and girls (P
.02 to 0.04). Models including dietary
calcium predicted 28% to 34% of variability
in body fat percentage.
Increases in consumption of fruit and lowfat
milk were associated with lower body fat
and lower body weight.

Zemel et al17

Randomized, placebo-controlled trial

for 24 weeks.
(SORT B, RCT but small sample size)

32 obese adults (27

women, 5 men)

Shapses et al18

Randomized placebo-controlled trial

for 25 weeks. Data combined from 3
separate trials.
(SORT B, RCT with larger sample
size, but not powered to detect
differences)

100 premenopausal and

postmenopausal
women

Drapeau et al15

Loos et al16

248 volunteers between

18 and 65 years old
(112 men, 136
women)
362 men (109 black, 253
white) and 462 women
(201 black, and 261
white)

Signicant inverse associations were found for

all men and white women between calcium
intake and percentage of body fat. There
was no signicant association seen in black
women.
All subjects were placed on a calorie-decient
diet. Then participants were randomized to
1 of 3 arms: standard diet, 400 to 500 mg
calcium with a placebo; high-calcium diet,
standard diet supplemented with 800 mg of
calcium; and high-dairy diet, 1200 to 1300
mg of dietary calcium with placebo
supplemented. Participants on the highdairy diet lost the most weight and the most
truncal fat. The participants on the high
calcium diet lost the second highest amount
and the participants on the standard diet lost
the least amount.
Subjects were randomized to receive either
1000 mg of calcium in a supplement or a
placebo. Weight loss was encouraged with
behavior modication and nutrition
education. Women participated in support
groups and a subset of postmenopausal
women was encouraged to consume one
third of their calories with a meal
replacement drink. There were no
signicant differences in body weight or
change in body fat between the 2 groups.

NHANES III, National Health and Nutrition Examination Study III; RCT, randomized control trial; BMI, body mass index; SORT,
strength of recommendation; RDA, recommended daily allowance; OR, odds ratio; RR, resistance ratio.

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Examination Study III (NHANES III) data and

found that after controlling for energy intake and
physical activity, body fat was lower in people with
the highest calcium intake. There was a reduction
in risk for obesity with each increasing quartile of
calcium intake. At the highest quartile of calcium
intake (an amount approximately equal to the current RDA for calcium), the risk of being in the
highest body mass index quartile was reduced by
85%.
Heaney et al11 reanalyzed data from 2 cohorts of
women studied from 1984 to 1985 and 1995
through 1997. These 348 women were enrolled in
studies examining calcium intake and bone density.
The young women at the 25th percentile of calcium intake for the group had a 15% prevalence of
overweight. Women in the group whose calcium
intake was equivalent to the current RDA for calcium had only a 4% prevalence of overweight. In
the second cohort of midlife women, a reduction in
average yearly weight gain was associated with increasing calcium intake.
Heaney et al12 also reanalyzed 6 observational
studies and 3 clinical trials that were originally
exploring dietary calcium intake and either bone
density or blood pressure as outcome measures.
This reanalysis found a consistent effect of higher
dietary calcium intake and either body fat, body
weight, or reduced midlife weight gain. In this
pooled data set, each 300-mg increase in daily calcium intake was associated with a 1-kg decrease in
body fat among children and a 2.5- to 3-kg decrease
in body weight in adults.
Davies et al13 reanalyzed 5 clinical studies of
calcium intake and bone density. The pooled data
set included 780 women in their 30s, 50s, or 80s.
Four of the studies were observational, and one was
a randomized controlled trial. There were signicant negative associations between calcium intake
and body weight. The odds ratio for being overweight in the young women was 2.25 for those
below the 50th percentile for calcium intakes. In
the controlled trial, women who received calcium
had a signicant weight loss over 4 years compared
with the placebo group. The authors extrapolated
that a 1000-mg difference in calcium intake is associated with a 8-kg difference in body weight and
that dietary calcium intake may explain approximately 3% of the change in weight.13
Several problems exist with data from reanalysis
of previous trials such as those above. First, some of

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the same studies were included in both of the above

reviews, which makes it hard to evaluate the results.12,13 Second, none of the trials were designed
with body weight as an endpoint. Therefore, unknown confounding factors may exist that effect the
data. Third, because the associations are derived
from observational studies, no evidence of causality
can be ascertained. For instance, it may be that the
people who ingested more calcium were also less
likely to eat at fast-food restaurants and were therefore less likely to be overweight or obese. In that
case, the calcium intake was caused not by the
lower risk of overweight or obesity but by another
factor entirely. It is also unclear whether calcium
itself has a major impact on body weight or whether
the impact comes from some other component of
dairy products.
Skinner et al14 demonstrated a negative relationship between dietary calcium intake and body fat in
a group of 8-year-old children in his prospective
study. In the authors statistical model, children
could reduce their body fat by 0.4% simply by
drinking an extra 8-oz glass of skim milk or 8 oz of
low-fat yogurt each day. The CARDIA prospective
study examined dairy consumption and several outcome variables associated with the IRS9 and found
an inverse relationship between dairy consumption
and all the components of the IRS, including obesity. The Quebec Family Study observed that calcium and dairy product intake induced changes in
body composition (ie, decreased abdominal circumference) in a long-term observational study.15
The Health, Risk Factors, Exercise, Training, and
Genetics (HERITAGE) Family Study, another
long-term prospective study, found signicant associations between low calcium intake and high
levels of adiposity in white and black men and white
women. These associations were not found in black
women.16

Prospective Studies in Humans

The epidemiologic evidence suggests a strong relationship between dietary calcium intake and
weight. However, there have been only 2 prospective controlled trials in humans using calcium supplementation as a variable and body weight as an
outcome. One of the studies found a signicant
relationship between calcium supplementation and
weight loss in people on a calorie-restricted diet17
whereas the other did not.18

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207

In their 2004 study, Zemel et al17 randomized 32

obese adults to a standard calorie-decient diet
alone, a calorie-decient diet supplemented with
calcium, or a calorie-decient diet supplemented
with dairy products. Participants lost 6.4% body
weight with the calcium-supplemented diet, 8.6%
with the standard diet, and 10.9% with the high
dairy diet (P .01). It is interesting that truncal fat
loss was signicantly augmented with calcium and
augmented even more by the high dairy diet (19%
of all fat lost on standard diet vs 50% of all fat lost
on calcium-supplemented diet vs 66% of all fat lost
on high-dairy diet, P .001).
Shapses et al18 performed 3 separate, randomized, placebo-controlled trials of 1000-mg calcium
supplementation in 100 premenopausal and postmenopausal women. There were no signicant differences between the calcium-supplemented group
and the placebo group in body weight or body fat.
Baseline calcium intakes ranged from 600 to 1000
mg per day in both groups. The calcium-supplemented groups calcium intakes averaged 1000 mg
more than the placebo group. Calcium supplementation in this trial did not accelerate weight loss.
There was, however, a small nonsignicant difference between the supplemented and placebo
groups in their mean total weight lost and the
proportion of weight lost as fat, with the supplemented group losing more weight and a higher
proportion of weight as fat.

Proposed Mechanisms of Action

There are 2 main physiologic mechanisms proposed to explain how calcium intake can affect body
weight or body fat. The rst is the effect of dietary
calcium on intracellular calcium levels in adipocytes, and the second is the effect of dietary calcium
on fatty acid absorption from the gastrointestinal
tract.
Effect of Dietary Calcium on Adipocytes
Ninety-nine percent of a bodys calcium content is
stored in the extracellular space. The majority of
extracellular calcium is stored in bones and teeth.
Intracellular cytosolic soluble calcium mediates
many metabolic pathways, including platelet aggregation and insulin resistance. Calcitropic hormones, such as parathyroid hormone (PTH) and
1,25-hydroxy vitamin D, regulate intracellular calcium. Low dietary calcium intake stimulates high

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levels of PTH and 1,25-hydroxy vitamin D, which

in turn stimulate high levels of intracellular calcium
in adipocytes stimulating lipogenesis and inhibiting
lipolysis. High dietary calcium intake depresses the
levels of PTH and 1,25-hydroxy vitamin D,
thereby causing lower levels of intracellular calcium
and inhibiting lipogenesis and stimulating lipolysis.19,20 Therefore, calcium intake may directly affect whether adipocytes store or break down fat.
Results of studies in transgenic mice are consistent with the preceding observations. High-calcium
diets were associated with a 51% decrease in adipocyte fatty acid synthase expression and activity
and a 3- to 5-fold increase in lipolysis in mice.20 In
mice subjected to calorie restriction, low-calcium
diets impeded body fat loss, and high-calcium diets
accelerated fat loss.20 All the mice on calciumsupplemented diets exhibited increased core temperature as well, whereas the mice on the plain
energy-restricted diet did not. A specic protein
(uncoupling protein 2) is up-regulated in the calcium-supplemented mice, which may cause increased
core temperature, although the mechanism of action is not clear.21

Change in Fat Absorption

The second proposed mechanism by which calcium
may impact body weight is that increased dietary
calcium seems to bind more fatty acids in the colon,
thereby inhibiting fat absorption. Welberg et al,22
in a small 1994 study, showed that calcium supplementation increased the percentage of excretion of
total fat as related to fat intake. The calcium supplementation in this study was either 2 or 4 g.
Denke et al23 supplemented 13 men with approximately 2 g of calcium per day in a 1993 study. The
percentage of dietary fat excreted per day increased
from 6% to 13% with calcium supplementation.
The Nestle Company supplemented chocolate
with 900 mg of calcium and tested the fecal fat
content of 10 men in a double-blind crossover
study. Calcium supplementation of chocolate increased fecal fat from 4.4 to 8.4 g per day (P
.0001).24 These studies show a small effect of calcium on fat absorption that probably contributes to
the antiobesity effects but does not explain it entirely. The degree of fecal fat loss in these studies of
high calcium supplementation is only approximately 3% of that induced by medications such as
orlistat.25

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Dairy versus Calcium Supplements

Several of the previously reviewed studies suggest
that calcium from dairy products affects weight loss
more than calcium derived from dietary supplements.17 Preliminary data point to some other
component in dairy products, possibly whey protein, effecting the weight-loss effect of calcium.26
Whey protein provides a multitude of bioactive
substances that may work synergistically with the
calcium to alter lipid metabolism.

3.

4.

5.

Implications for Primary Care Providers

Calcium is not a magic bullet in the battle against
obesity, although it may play a small, but signicant, role. The affect of dairy products or calcium is
probably greatest in those people whose adipocyte
status is changing, such as during weight loss, ageassociated weight gain, and growth.27 Women, in
particular, are at high risk for age-associated weight
gain after menopause. Calcium contributes to
maintenance of strong bones and may modulate
weight gain in postmenopausal women. As such,
primary care providers can target postmenopausal
women and overweight or obese adults and children for extra counseling about calcium intake.
(Strength of Recommendation level C: expert opinion.28) An important concept to remember is that
calcium does not seem to be effective unless a
calorie restriction is already in place. Replacing
other sources of protein with low-fat dairy products
may help augment weight loss. Adequate calcium
intake, preferably from dairy products, may be especially important in people who have hypertension or components of the IRS. All patients should
be encouraged to consume 3 to 4 servings of lowfat dairy products every day. Primary care providers
should include recommendations about calcium intake in standard dietary counseling about weight
management.

6.

7.

8.

9.

10.

11.

12.

13.

14.

15.

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