Is it a Sin for a Christian Not to Live a Healthy Lifestyle?

Is it a sin for a Christian not to have a regimented diet and exercise program with the intended purpose of living as long as they possible can?  Many Christians believe this.   But the Bible had different definition of health than the world does.

This is part of three of my series on fitism.  In the first part of my series, I defined fitism as the belief that a requirement of godliness is that Christians must have regimented diet and exercise programs which should result in having toned bodies and flat stomachs.

Now some fitists reading this series were probably screaming “It’s not just about how you look – its about your heath!”  And in this third part of my series, I will address the health argument that fitists try to make.

Christian Fitists Cling to a Worldly Definition of “Health”

Jesus didn’t tell us to live by “every study that comes from the scientific community”, but rather he told us to live by “every word that proceedeth out of the mouth of God” (Matthew 4:4). 

It is a bit ironic that many traditional Christians have correctly rejected “scientific consensus” about the efficacy of the covid vaccines or the need for “gender affirming” surgeries yet when it comes to what is healthy weight they accept “scientific consensus” as gospel truth.

The “obesity epidemic” was declared by the CDC in the late 1990s.  It followed the fitness movement which started in the late 70s and early 80s.  Scientific studies began to be produced to promote the BMI (Body Mass Index) model as the central focus of human health.

When studies in the 2000’s emerged that began to question the BMI model as the central determining factor of one’s future health many in the scientific and medical community refused to hear this.  In their minds, the science around the effects of weight and obesity were settled.

Some studies in the 2000’s and 2010’s showed that a large percent of people who were classified as overweight or even moderately obese where actually healthier than those who fell in the normal BMI range.

See “Why Scientists Can’t Agree on Whether It’s Unhealthy to Be Overweight” (Is It Unhealthy to Be Overweight? – The Atlantic) from the Atlantic which has a pretty good summary of the debate between Scientists on this issue.

As Christians we must understand that the CDC BMI categories for “Underweight”, “Healthy Weight”, “Overweight”, “Obese” and “Morbidly Obese” (40+) are not the Biblical definition of health. These categories represent the opinions of one side.  And there is another side.

It is absolutely truth that there are some people who have unhealthy weights due to being underweight or weighing too much.  But the definition of what should be considered normal healthy weight is much larger than BMI shows today. 

A General Biblical Definition of Health

In 3 John 1:2 the Bible says the following:

 “Beloved, I wish above all things that thou mayest prosper and be in health even as thy soul prospereth”.

What was the Apostle John, writing under the inspiration of the Holy Spirit, wishing for believers when said “be in health”?

Believers in fitism see the phrase “be in health” as meaning “Make sure you eat a balanced diet of only organic foods and that your physical activity and your calorie intake results in a BMI that stays between 18.5 to 24.9 and you maintain a flat stomach with a toned body”.

But when we take 3 John 1:2 as a whole, it is more likely that John is praying that God would grant the believers financial prosperity and God would not allow them to get sick rather than hoping they would follow some regimented dietary and exercise program

If God was prescribing through John that Christians have a regimented diet and exercise plan, he would not have said in 1 Timothy 4:8 “bodily exercise profiteth little” nor would he have said in Romans 14:17 “For the kingdom of God is not meat and drink; but righteousness…”

The Bible says in Proverbs 3:1 & 6 & 8 “My son, forget not my law; but let thine heart keep my commandments… Trust in the Lord with all thine heart; and lean not unto thine own understanding… It shall be health to thy navel, and marrow to thy bones”.

And in Proverbs 17:22 the Bible says “A merry heart doeth good like a medicine: but a broken spirit drieth the bones” and Proverbs 14:30 says “A sound heart is the life of the flesh: but envy the rottenness of the bones”. 

The Biblical prescription for having good health is not a regimented diet and exercise program always aiming to keep a particular weight and aesthetic.  Instead, the Bible teaches us that following God’s law, trusting in God and having a joyful and content heart are the most important factors in keeping one’s health.


As a husband and father, you may choose to base your decision as to what constitutes a healthy body weight for yourself, your wife and your children on CDC BMI guidelines. But what you should not do is judge or teach your family to judge other families who do not accept this.

If you as a husband and father want to add a more regimented diet and exercise program for your wife and children in addition to encouraging them to follow God’s commands, to trust God and have joyful and content hearts there certainly are benefits to this.

But we as husbands and fathers should never lead our wives and children to believe that our health is solely dependent upon diet and exercise.  The Scriptures make clear that maintaining a right mental and spiritual outlook is the foundation for having good health.

In my next part of this series on fitism we will discuss specific principles which will help a Christian man to determine if he is indeed healthy in the eyes of God.

Click here to go the next part of this series

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