Unsweetened coffee linked to weight loss, study reveals

A recent study published in The American Journal of Clinical Nutrition finds that an increase in unsweetened coffee consumption reduces the risk of body weight gain.

Study: Changes in Coffee Intake, Added Sugar and Long-Term Weight Gain – Results from Three Large Prospective US Cohort Studies. Image Credit: i love coffee / Shutterstock.com

Background

Daily coffee consumption can reduce the risk of chronic diseases, including cardiovascular disease, type 2 diabetes, obesity, and certain cancers. Coffee consumption also reduces disease-specific and all-cause mortalities. Evidence indicates that coffee exerts health benefits mainly by activating the sympathetic nervous system and increasing energy expenditure.

Coffee is often consumed with added sugar, artificial sweeteners, or creamer. These ingredients are associated with various adverse health effects, including body weight gain. Previous studies have suggested that the addition of these ingredients to coffee may attenuate the metabolic health benefits associated with consuming coffee.

In the current study, scientists examine the relationship between changes in coffee consumption, caffeine intake, and changes in body weight gain by considering the addition of sugar, cream, or non-dairy creamer to coffee.   

Study design

Data were obtained from three extensive prospective cohort studies, including the Nurses’ Health Study (1986-2010), Nurses’ Health Study II (1991-2015), and the Health Professional Follow-up Study (1991-2014).

All study participants completed questionnaires that were used to assess food and beverage intake over the previous year at baseline and every four years during follow-up visits. The consumption of both decaffeinated and caffeinated coffee, as well as the habits of adding sugar, cream, and non-sweeteners to coffee, were considered in the analyses.

Appropriate statistical analyses were performed to assess the relationship between coffee consumption changes and concurrent body weight changes during each four-year period.

Important observations

A total of 48,891 participants from the Nurses’ Health Study, 83,464 participants from the Nurses’ Health Study II, and 22,863 participants from the Health Professional Follow-up Study were included in the analysis. The average four-year weight gain in these cohorts was 1.2, 1.7, and 0.8 kg, respectively. The differences in participants’ age and sex might be responsible for the observed differences in weight gain among these cohorts.

A minimal change in coffee consumption overall four-year periods was observed in each cohort. More specifically, the change was about two cups each day.

No change in the average baseline level of adding sugar was observed over the four-year periods. Over 80% of the study participants reported not changing their habit of adding sugar over the study period.

Association between coffee consumption and body weight change

The analysis of average changes in coffee consumption and body weight over four years revealed that an increase of one cup of unsweetened caffeinated or decaffeinated coffee daily is associated with a moderate reduction in weight gain of about 0.12 kg.

Comparatively, an increase in adding one teaspoon of sugar to any food or beverage each day was associated with a weight gain of 0.09 kg over the four-year period. No significant association was observed between adding cream or non-dairy creamer and weight gain.

The observed associations between changes in coffee or added sugar consumption and body weight changes were more pronounced among overweight or obese participants and younger participants.

Considering caffeine consumption separately, the current study revealed that an increase in caffeine intake by 100 mg daily is associated with a reduction in weight gain by 0.08 kg. These findings were similar to those observed for caffeinated coffee.

The robustness of all observed associations was further confirmed by sensitivity analyses, which adjusted for certain dietary variables, including changes in the intake of fruits, vegetables, grains, fibers, meat, fish, eggs, and dairy products.

No changes in the observed associations were reported after excluding participants who added more than five teaspoons of sugar to foods or beverages or after restricting the analyses to participants who drank at least one cup of coffee at the beginning and at the end of each four-year period.

Study significance

Increasing the consumption of unsweetened caffeinated or decaffeinated coffee might be effective for body weight management. However, adding sugar to coffee can largely attenuate the health benefits of coffee consumption.