- an adult that has a BMI between 25 and 29.9 is considered overweight
- an adult that has a BMI of 30 or more is considered obese
So, back to the obesity statistics. This may not be all that surprising to some, but it's a sad fact that recent data released by the Weight Control Information Network (WIN) shows that over one third (33.8%) of American adults (age > 20) are obese and over two thirds (68%) are overweight. After checking your BMI, you might even be realizing that you're among these statistics.
Okay, enough of the depressing news. Let's talk about what can be done to make a positive change in these obesity trends. The last post mentioned the 1990's low-fat/no-fat diet craze. Then the pendulum swung the other way and low carbohydrate eating became the next fad. Regardless of how or what you're eating, the most important information to keep in mind when you're trying to lose weight is calorie consumption. If the calories being consumed are greater than the calories being burned, weight gain occurs. It's as simple as that.
Most experts agree that 20-35% of our daily calories should come from fat This amounts to about 44 to 78 grams of total fat a day, based on a 2,000 calorie a day diet (Mayo Clinic). Even though all fats contain the same number of calories (9 calories per gram), it's the foods we eat and the types of fat they provide that is vitally important. In addition, the ratio of certain fats in our diet is being recognized as significant for good health as well.
Unsaturated fats - the good
These fats are called unsaturated because of their chemical structure, where most of the fatty acids are not saturated with hydrogens. You may recall that unsaturated fats can be mono- or polyunsaturated fatty acids (also known as MUFA's and PUFA's respectively). Major sources of MUFA's are:
- plants oils ( olive oil, peanut oil, canola oil)
- avocados, nuts and seeds
- plant oils (safflower, sesame, soy, corn and sunflower)
- nuts and seeds
- high in omega 3 - Fatty, cold-water fish (such as salmon, mackerel and herring), flax seeds, flax oil and walnuts
In addition to fats that are unsaturated, there are also fats that are saturated. They are called saturated fatty acids because their chemical structure has all the hydrogens it can hold, so it is said to be saturated. Later in the post the significance of the hydrogen saturation/unsaturation will become clearer, but for now it's important to note that saturated fats should be limited in the diet. Consuming saturated fat is one of the main dietary factors linked to increased blood (serum) cholesterol levels. Major sources of saturated fats are:
- whole milk, cream, butter, cheese,
- fatty cuts of beef and pork, sausage
- coconut, palm and palm kernel oils and products containing them like prepackaged cakes, cookies, pies, doughnuts and pastries
The fact that a fat is saturated, or mono/polyunsaturated influences its firmness at room temperature and also its stability. Generally speaking, an example would be that polyunsaturated vegetable oils are liquid, whereas saturated fats like that found in beef or butter are more solid. All fats eventually become spoiled (rancid) when exposed to oxygen (oxidation), but polyunsaturated fats are the most unstable, so they're the most susceptible.
Back in the early 1900's a chemist figured out a way to alter the chemical structure of fats through a process called hydrogenation. This is the chemical process of taking a mono- or polyunsaturated fat and partially saturating it with more hydrogen atoms. Why bother? Well, one reason behind hydrogenation is that it makes a liquid fat more solid. It also increases the stability of the fat. This helps to prevent spoilage and extends the shelf life of prepackaged foods containing partially hydrogenated oils. Unfortunately, the downside of this process results in what are called trans-fatty acids, which are also known as trans-fats. Major sources of trans-fats are:
- Commercial baked goods — such as crackers, cookies and cakes
- Fried foods, such as doughnuts and french fries
- Shortenings and some margarine can be high in trans fat (Mayo Clinic)
So, now that we're familiar with the types of fat, and a few of the food sources, how can we apply this knowledge? How can we consume more of the good fats and in the proper ratios? The next and final post on fats will cover these questions. In the meantime, one suggestion is to avoid or eliminate processed, prepackaged (short for prepared and packaged) and fast foods which contain the bad and ugly fats. Replace these with whole foods, which are in their natural state, or have been processed or refined as little as possible. Start by trying to make small dietary changes, like substituting a serving of omega 3 rich fish for meat once a week. Taking small steps does make a difference and can eventually lead to lifestyle changes and healthier nutrition.
Image source: Merriam Webster