A new study reveals that drastically restricting your carbohydrate and fat intake may shorten your life

A new study suggests that extreme eating habits involving low carb intake in men and higher carb intake in women are associated with a higher risk of death. However, higher fat intake in women may reduce the risk of all-cause and cancer-related deaths, highlighting the need for a balanced diet.

A new study published in nutrition journal, It indicates that extreme eating patterns associated with fats and carbohydrates can affect longevity. The research, conducted by Dr. Takashi Tamura of Nagoya University School of Medicine in Japan, reveals that men who consume low amounts of carbohydrates and women who consume high amounts of carbohydrates face an increased risk of overall cancer-related death. In addition, the study suggests that women who consume more fat may have a lower risk of death from any cause.

Their findings suggest that people should eat a balanced diet rather than drastically restricting their intake of carbohydrates or fats.

While low-carb and low-fat diets have become popular as a way to promote weight loss and improve blood glucose levels, their long-term effects on life expectancy are less clear. Interestingly, recent studies conducted in Western countries indicate that extreme dietary habits regarding carbohydrates and fats are associated with a higher risk of death. However, few studies have explored these associations in East Asian populations, including Japanese individuals who typically have a relatively low fat and high carbohydrate dietary intake.

The authors conducted a 9-year follow-up survey with 81,333 Japanese subjects (34,893 men and 46,440 women) to assess the relationship between carbohydrate and fat intake and risk of death. Daily dietary intake of carbohydrates, fats, and total energy was estimated using a food frequency questionnaire and calculated as a percentage of total energy intake for carbohydrates and fats.

Quality of carbohydrate intake (that is, refined compared to intake of minimally processed carbohydrates) and quality of fat intake (ie, saturated compared to intake of unsaturated fats) were also assessed to examine the effect of dietary quality on the association with mortality.

They found that men who consumed less than 40% of their total energy from carbohydrates had a significantly higher risk of all-cause and cancer-related deaths. This trend was observed regardless of whether refined or minimally processed carbohydrates were taken into account. On the other hand, among women with 5 or more years of follow-up, those with a higher carbohydrate intake were more than 65% more likely to die from all causes. No clear association was observed between the intake of refined or minimally processed carbohydrates and the risk of death in women.

For fat, men with a high fat intake of more than 35% of their total energy from fat had a higher risk of cancer-related death. They also found that lower intake of trans fats in men was associated with a higher risk of all-cause and cancer-related deaths. In contrast, the women’s total fat and saturated fat intake showed an inverse relationship with the risk of all-cause mortality and cancer-related mortality. They concluded that this finding does not support the idea that high fat intake is detrimental to longevity in women.

“The finding that saturated fat intake is inversely associated with risk of death in women only may partially explain the differences in the associations between the sexes,” said Dr. Tamura. “Alternatively, components other than fat in dietary sources of fat may be responsible for the observed inverse association between fat intake and mortality in women.”

This study is very important because restricting carbohydrates and fats, such as low-carb and low-fat diets, are now popular diet strategies aimed at improving health, including managing metabolic syndrome. However, this study shows that low-carb and low-fat diets may not be the healthiest strategy for promoting longevity, as their short-term benefits can be outweighed by their long-term risks.

In general, an unfavorable relationship with mortality was observed for low-carbohydrate intake in men and high-carbohydrate intake for women, while high-fat intake could be associated with a lower risk of death in women. The findings suggest that individuals should carefully consider how they balance their diet and ensure that they obtain energy from a variety of food sources while avoiding extremes.

Reference: “Intake of Carbohydrates and Dietary Fats and Risk of Mortality among the Japanese Population: A Multi-Institutional Collaborative Cohort Study in Japan” by Takashi Tamura, Kenji Wakai, Yasofumi Kato, Yudai Tamada, Yoko Kubo, Reiko Okada, Mako Nagayoshi, Asahi Hishida. Nahumi Imaeda, Chiho Goto, Hiroaki Ikezaki, Jun Otonari, Megumi Hara, Keitaro Tanaka, Yohko Nakamura, Miho Kusakabe, Rei Ibusuke, Chihaya Kuriyama, Isao Oze, Hidemi Ito and Keitaro Matsuo, June 2, 2023, Nutrition magazine.
doi: 10.1016/j.tjnut.2023.05.027